From the lead author of the international bestseller Limits to Growth 来自国际畅销书《增长的极限》的主要作者
Thinking in Systems
A Primer 系统思维入门
Thinking in Systems 系统思考
Other Books by Donella H. Meadows: Donella H. Meadows 的其他书籍：
Harvesting One Hundredfold: Key Concepts and Case Studies in Environmental Education (1989). The Global Citizen (1991). with Dennis Meadows: Toward Global Equilibrium (1973). 收获百倍：环境教育的关键概念和案例研究》（1989 年）。全球公民》（1991 年），与 Dennis Meadows 合著：Toward Global Equilibrium》（1973 年）。
with Dennis Meadows and Jørgen Randers: 丹尼斯-梅多斯和约根-兰德斯：
Beyond the Limits (1992). 超越极限》（1992 年）。
Limits to Growth: The 30-Year Update (2004). 增长的极限》：30 年更新》（2004 年）。
with Dennis Meadows, Jørgen Randers, and William W. Behrens III: The Limits to Growth (1972). 与 Dennis Meadows、Jørgen Randers 和 William W. Behrens III 合著：《增长的极限》（1972 年）。
with Dennis Meadows, et al.: 与 Dennis Meadows 等人合作：
The Dynamics of Growth in a Finite World (1974). 有限世界中的增长动力》（1974 年）。
WITH J. RICHARDSON AND G. BRUCKMANN: 与J.理查德森和G.布吕克曼：
Groping in the Dark: The First Decade of Global Modeling (1982). 在黑暗中摸索：全球建模的第一个十年》（1982 年）。
WITH J. Robinson: WITH J. Robinson：
The Electronic Oracle: Computer Models and Social Decisions (1985). The Electronic Oracle：计算机模型与社会决策》（1985 年）。
Thinking in Systems 系统思考
A Primer — 初级读本
Donella H. Meadows
Edited by Diana Wright, 编辑：戴安娜-赖特
Sustainability Institute 可持续发展研究所
publishing for a sustainable future 为可持续的未来而出版
LONDON STERLING, VA 伦敦 弗吉尼亚州斯特林
First published by Earthscan in the UK in 2009 Earthscan 于 2009 年在英国首次出版
Copyright by Sustainability Institute. 可持续发展研究所版权所有。
All rights reserved 保留所有权利
ISBN: 978-1-84407-726-7 (pb)
ISBN: 978-1-84407-725-0 (hb)
Typeset by Peter Holm, Sterling Hill Productions 排版：彼得-霍尔姆，斯特林山制作公司
Cover design by Dan Bramall 封面设计：Dan Bramall
For a full list of publications please contact: 如需完整的出版物清单，请联系
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Earthscan publishes in association with the International Institute for Environment and Development Earthscan 与国际环境与发展研究所联合出版
A catalogue record for this book is available from the British Library 大英图书馆可提供此书的目录记录
Library of Congress Cataloging-in-Publication Data has been applied for. 已申请美国国会图书馆编目出版数据。
At Earthscan we strive to minimize our environmental impacts and carbon footprint through reducing waste, recycling and offsetting our emissions, including those created through publication of this book. For more details of our environmental policy, see www.earthscan.co.uk. 在 Earthscan，我们通过减少废物、循环利用和抵消 排放物（包括出版本书所产生的排放物），努力将我们对环境的影响和碳足迹降至最低。有关我们环境政策的更多详情，请参阅 www.earthscan.co.uk。
This book was printed in the UK by TJ International Ltd, an ISO 14001 accredited company. The paper used is FSC certified. 本书由获得 ISO 14001 认证的 TJ 国际有限公司在英国印刷。所使用的纸张通过了 FSC 认证。
Part of this work has been adapted from an article originally published under the title "Whole Earth Models and Systems" in Coevolution Quarterly (Summer 1982). An early version of Chapter 6 appeared as "Places to Intervene in a System" in Whole Earth Review (Winter 1997) and later as an expanded paper published by the Sustainability Institute. Chapter 7, "Living in a World of Systems," was originally published as "Dancing with Systems" in Whole Earth Review (Winter 2001). 本文部分内容改编自最初发表在《共同进化季刊》（1982 年夏）上的一篇文章，标题为 "全地球模型与系统"。第 6 章的早期版本以 "介入系统的地点 "为题发表在《整个地球评论》（1997 年冬）上，后来作为扩展论文由可持续发展研究所出版。第 7 章 "生活在系统的世界中 "最初以 "与系统共舞 "为题发表于《整个地球评论》（2001 年冬）。
FOR DANA 给达纳
(1941-2001)
and for all those who would learn from her 以及所有向她学习的人
CONTENTS 目 录
A Note from the Author | ix 作者说明 | ix
A Note from the Editor xi 编者的话 xi
Introduction: The Systems Lens 导言：系统透镜
Part One: System Structures and Behavior 第一部分：系统结构和行为
ONE. The Basics 一个基础知识
TWO. A Brief Visit to the Systems Zoo | 35 TWO.对系统动物园的简短访问 | 35
Part Two: Systems and Us 第二部分：系统与我们
THREE. Why Systems Work So Well 三.系统为何如此有效
FOUR. Why Systems Surprise Us 86 4.为什么系统会给我们带来惊喜 86
FIVE. System Traps . . and Opportunities | 111 系统陷阱.系统陷阱......与机遇 | 111
Part Three: Creating Change-in Systems and in Our Philosophy 第三部分在系统和我们的理念中创造变革
SIX. Leverage Points-Places to Intervene in a System | 145 六.杠杆点--干预系统的位置 | 145
SEVEN. Living in a World of Systems | 166 七.生活在系统世界中 | 166
Appendix 附录
System Definitions: A Glossary | 187 系统定义：词汇表 | 187
Summary of Systems Principles | 188 系统原理摘要
Springing the System Traps | 191 跳出系统陷阱 | 191
Places to Intervene in a System | 194 干预系统的位置 | 194
Guidelines for Living in a World of Systems | 194 生活在系统世界中的指南 | 194
Model Equations | 195 模型方程 | 195
Notes | 204 注释
Bibliography of Systems Resources | 208 系统资源参考书目 | 208
Editor's Acknowledgments | 211 编辑致谢 | 211
About the Author 关于作者
Index 索引
A NOTE FROM THE AUTHOR 作者手记
This book has been distilled out of the wisdom of thirty years of systems modeling and teaching carried out by dozens of creative people, most of them originally based at or influenced by the MIT System Dynamics group. Foremost among them is Jay Forrester, the founder of the group. My particular teachers (and students who have become my teachers) have been, in addition to Jay: Ed Roberts, Jack Pugh, Dennis Meadows, Hartmut Bossel, Barry Richmond, Peter Senge, John Sterman, and Peter Allen, but I have drawn here from the language, ideas, examples, quotes, books, and lore of a large intellectual community. I express my admiration and gratitude to all its members. 本书是数十位富有创造力的人士三十年系统建模和教学智慧的结晶，他们中的大多数人最初都在麻省理工学院系统动力学小组工作，或受到该小组的影响。其中最重要的是该小组的创始人杰伊-福雷斯特（Jay Forrester）。除了杰伊之外，我的老师（以及成为我老师的学生）还包括埃德-罗伯茨（Ed Roberts）、杰克-普（Jack Pugh）、丹尼斯-米多斯（Dennis Meadows）、哈特穆特-博塞尔（Hartmut Bossel）、巴里-里士满（Barry Richmond）、彼得-圣吉（Peter Senge）、约翰-斯特曼（John Sterman）和彼得-艾伦（Peter Allen）。我向所有成员表示钦佩和感谢。
I also have drawn from thinkers in a variety of disciplines, who, as far as I know, never used a computer to simulate a system, but who are natural systems thinkers. They include Gregory Bateson, Kenneth Boulding, Herman Daly, Albert Einstein, Garrett Hardin, Václav Havel, Lewis Mumford, Gunnar Myrdal, E.F. Schumacher, a number of modern corporate executives, and many anonymous sources of ancient wisdom, from Native Americans to the Sufis of the Middle East. Strange bedfellows, but systems thinking transcends disciplines and cultures and, when it is done right, it overarches history as well. 据我所知，他们从未使用过计算机模拟系统，但他们都是自然系统思想家。他们包括格雷戈里-贝特森（Gregory Bateson）、肯尼斯-博尔丁（Kenneth Boulding）、赫尔曼-戴利（Herman Daly）、阿尔伯特-爱因斯坦（Albert Einstein）、加勒特-哈丁（Garrett Hardin）、瓦茨拉夫-哈维尔（Václav Havel）、刘易斯-芒福德（Lewis Mumford）、贡纳尔-米达尔（Gunnar Myrdal）、E.F. 舒马赫（E.F. Schumacher）、一些现代企业高管，以及从美洲原住民到中东苏菲派等许多无名的古代智慧来源。这些都是奇怪的伙伴，但系统思维超越了学科和文化，如果运用得当，它还能超越历史。
Having spoken of transcendence, I need to acknowledge factionalism as well. Systems analysts use overarching concepts, but they have entirely human personalities, which means that they have formed many fractious schools of systems thought. I have used the language and symbols of system dynamics here, the school in which I was taught. And I present only the core of systems theory here, not the leading edge. I don't deal with the most abstract theories and am interested in analysis only when I can see how it helps solve real problems. When the abstract end of systems theory does that, which I believe it will some day, another book will have to be written. 在谈到超越性之后，我还需要承认派别纷争。系统分析师使用的是总体概念，但他们完全是人云亦云，这意味着他们形成了许多纷争不断的系统思想流派。我在这里使用的是系统动力学的语言和符号，这也是我所受教育的流派。我在这里介绍的只是系统理论的核心，而不是前沿。我不涉及最抽象的理论，只有当我能看到分析如何帮助解决实际问题时，我才会对分析感兴趣。当系统理论的抽象部分做到这一点时（我相信总有一天会做到的），就需要写另一本书了。
Therefore, you should be warned that this book, like all books, is biased and incomplete. There is much, much more to systems thinking than is 因此，需要提醒大家的是，本书和其他所有书籍一样，是有失偏颇和不完整的。系统思维的内涵远不止这些。
presented here, for you to discover if you are interested. One of my purposes is to make you interested. Another of my purposes, the main one, is to give you a basic ability to understand and to deal with complex systems, even if your formal systems training begins and ends with this book. 如果你有兴趣，可以在这里找到。我的目的之一就是让你感兴趣。我的另一个目的，也是最主要的目的，是让你具备理解和处理复杂系统的基本能力，即使你的正规系统培训始于本书，也止于本书。
A NOTE FROM THE EDITOR 编者的话
In 1993, Donella (Dana) Meadows completed a draft of the book you now hold. The manuscript was not published at the time, but circulated informally for years. Dana died quite unexpectedly in 2001-before she completed this book. In the years since her death, it became clear that her writings have continued to be useful to a wide range of readers. Dana was a scientist and writer, and one of the best communicators in the world of systems modeling. 1993 年，Donella (Dana) Meadows 完成了您现在手中这本书的草稿。手稿当时没有出版，但非正式流传了多年。2001 年，丹娜在完成这本书之前意外去世。在她去世后的这些年里，我们发现她的著作对广大读者仍然有用。丹娜是一位科学家和作家，也是系统建模领域最优秀的传播者之一。
In 1972, Dana was lead author of The Limits to Growth - a best-selling and widely translated book. The cautions she and her fellow authors issued then are recognized today as the most accurate warnings of how unsustainable patterns could, if unchecked, wreak havoc across the globe. That book made headlines around the world for its observations that continual growth in population and consumption could severely damage the ecosystems and social systems that support life on earth, and that a drive for limitless economic growth could eventually disrupt many local, regional, and global systems. The findings in that book and its updates are, once again, making front-page news as we reach peak oil, face the realities of climate change, and watch a world of 6.6 billion people deal with the devastating consequences of physical growth. 1972 年，丹娜是畅销书《增长的极限》（The Limits to Growth）的主要作者，该书被广泛翻译。她和其他作者当时发出的警告被认为是最准确的警示，告诉人们如果不加以控制，不可持续的模式会给全球带来怎样的灾难。这本书成为了全世界的头条新闻，因为书中指出，人口和消费的持续增长可能会严重破坏支持地球生命的生态系统和社会系统，无限的经济增长动力最终可能会破坏许多地方、地区和全球系统。随着石油峰值的到来，面对气候变化的现实，以及眼看着一个拥有 66 亿人口的世界要应对物质增长带来的破坏性后果，该书及其更新版中的发现再次成为头版新闻。
In short, Dana helped usher in the notion that we have to make a major shift in the way we view the world and its systems in order to correct our course. Today, it is widely accepted that systems thinking is a critical tool in addressing the many environmental, political, social, and economic challenges we face around the world. Systems, big or small, can behave in similar ways, and understanding those ways is perhaps our best hope for making lasting change on many levels. Dana was writing this book to bring that concept to a wider audience, and that is why I and my colleagues at the Sustainability Institute decided it was time to publish her manuscript posthumously. 简而言之，达纳帮助我们树立了这样一种观念，即我们必须在看待世界及其系统的方式上做出重大转变，才能纠正我们的方向。如今，人们普遍认为，系统思维是解决我们在世界各地面临的诸多环境、政治、社会和经济挑战的重要工具。系统，无论大小，都有相似的行为方式，而理解这些方式或许是我们在多个层面上实现持久变革的最大希望。达娜写这本书的目的就是要将这一理念带给更多的读者，这也是我和可持续发展研究所的同事们决定在她去世后出版她的手稿的原因。
Will another book really help the world and help you, the reader? I think 另一本书真的会对世界和读者有所帮助吗？我认为
so. Perhaps you are working in a company (or own a company) and are struggling to see how your business or organization can be part of a shift toward a better world. Or maybe you're a policy maker who is seeing others "push back" against your good ideas and good intentions. Perhaps you're a manager who has worked hard to fix some important problems in your company or community, only to see other challenges erupt in their wake. As one who advocates for changes in how a society (or a family) functions, what it values and protects, you may see years of progress easily undone in a few swift reactions. As a citizen of an increasingly global society, perhaps you are just plain frustrated with how hard it is to make a positive and lasting difference. 所以。也许你在一家公司工作（或拥有一家公司），正在苦苦思索你的企业或组织如何才能成为向更美好世界转变的一部分。又或者，你是一位政策制定者，看到别人 "回击 "你的好想法和好意图。也许你是一位管理者，努力解决了公司或社区的一些重要问题，但却看到其他挑战随之而来。作为一个倡导改变社会（或家庭）运作方式、价值观念和保护措施的人，你可能会看到多年来取得的进步很容易被一些迅速的反应所抵消。作为一个日益全球化的社会的公民，也许你只是单纯地感到沮丧，因为要做出积极而持久的改变是多么困难。
If so, I think that this book can help. Although one can find dozens of titles on "systems modeling" and "systems thinking," there remains a clear need for an approachable and inspiring book about systems and us-why we find them at times so baffling and how we can better learn to manage and redesign them. 如果是这样，我想这本书会有所帮助。尽管我们可以找到几十种关于 "系统建模 "和 "系统思考 "的书籍，但我们仍然明显需要一本关于系统和我们的平易近人、鼓舞人心的书籍--为什么我们有时会发现它们如此令人困惑，以及我们如何才能更好地学会管理和重新设计它们。
At the time that Dana was writing Thinking in Systems, she had recently completed the twenty-year update to Limits to Growth, titled Beyond the Limits. She was a Pew Scholar in Conservation and the Environment, was serving on the Committee on Research and Exploration for the National Geographic Society, and she was teaching about systems, environment, and ethics at Dartmouth College. In all aspects of her work, she was immersed in the events of the day. She understood those events to be the outward behavior of often complex systems. 在丹娜撰写《系统思考》一书时，她刚刚完成了《增长的极限》的二十年更新版《超越极限》。她是皮尤保护与环境学者，在国家地理学会研究与探索委员会任职，并在达特茅斯学院讲授系统、环境和伦理学。在她工作的各个方面，她都沉浸在当时发生的事件中。她将这些事件理解为往往是复杂系统的外在行为。
Although Dana's original manuscript has been edited and restructured, many of the examples you will find in this book are from her first draft in 1993. They may seem a bit dated to you, but in editing her work I chose to keep them because their teachings are as relevant now as they were then. The early 1990s were the time of the dissolution of the Soviet Union and great shifts in other socialist countries. The North American Free Trade Agreement was newly signed. Iraq's army invaded Kuwait and then retreated, burning oil fields on the way out. Nelson Mandela was freed from prison, and South Africa's apartheid laws were repealed. Labor leader Lech Walesa was elected president of Poland, and poet Václav Havel was elected president of Czechoslovakia. The International Panel on Climate Change issued its first assessment report, concluding that "emissions from human activities are substantially increasing the atmospheric concentra- 虽然达娜的原稿已经过编辑和调整，但你在本书中看到的许多例子都来自她 1993 年的初稿。你可能会觉得这些例子有些过时，但在编辑她的作品时，我选择了保留它们，因为它们的教诲现在和当时一样具有现实意义。20 世纪 90 年代初，苏联解体，其他社会主义国家也发生了巨大变化。北美自由贸易协定》刚刚签署。伊拉克军队入侵科威特，随后撤退，途中焚烧油田。纳尔逊-曼德拉获释出狱，南非种族隔离法被废除。工党领袖莱赫-瓦文萨当选波兰总统，诗人瓦茨拉夫-哈维尔当选捷克斯洛伐克总统。国际气候变化专门委员会发布了第一份评估报告，得出结论认为 "人类活动的排放正在大幅增加大气中的温室气体浓度"。
tions of greenhouse gases and that this will enhance the greenhouse effect and result in an additional warming of the Earth's surface." The UN held a conference in Rio de Janeiro on environment and development. 联合国在里约热内卢召开了关于环境与发展的会议。联合国在里约热内卢召开了环境与发展会议。
While traveling to meetings and conferences during this time, Dana read the International Herald Tribune and during a single week found many examples of systems in need of better management or complete redesign. She found them in the newspaper because they are all around us every day. Once you start to see the events of the day as parts of trends, and those trends as symptoms of underlying system structure, you will be able to consider new ways to manage and new ways to live in a world of complex systems. In publishing Dana's manuscript, I hope to increase the ability of readers to understand and talk about the systems around them and to act for positive change. 在这段时间里，丹娜在参加各种会议的旅途中阅读了《国际先驱论坛报》，并在一周内发现了许多需要更好管理或完全重新设计的系统实例。她之所以在报纸上发现这些例子，是因为它们每天都在我们身边发生。一旦你开始把每天发生的事件看作是趋势的一部分，把这些趋势看作是潜在系统结构的表征，你就能在复杂的系统世界中考虑新的管理方法和新的生活方式。通过出版丹娜的手稿，我希望能提高读者理解和谈论他们周围系统的能力，并为积极的变革采取行动。
I hope this small approachable introduction to systems and how we think about them will be a useful tool in a world that rapidly needs to shift behaviors arising from very complex systems. This is a simple book for and about a complex world. It is a book for those who want to shape a better future. 我希望这本关于系统和我们如何思考系统的平易近人的小册子，能够成为一个有用的工具，帮助这个世界迅速转变由非常复杂的系统产生的行为。这是一本为复杂世界而写的简单的书，也是一本关于复杂世界的简单的书。这本书适合那些希望塑造更美好未来的人阅读。
-Diana Wright, 2008 戴安娜-赖特，2008 年
If a factory is torn down but the rationality which produced it is left standing, then that rationality will simply produce another factory. If a revolution destroys a government, but the systematic patterns of thought that produced that government are left intact, then those patterns will repeat themselves.... There's so much talk about the system. And so little understanding. 如果一家工厂被拆毁，但生产它的理性却屹立不倒，那么这种理性只会生产出另一家工厂。如果一场革命摧毁了一个政府，但产生这个政府的系统思维模式却完好无损地保留了下来，那么这些模式就会自我重复....。关于系统的讨论太多了。却很少有人了解。
-Robert Pirsig, Zen and the Art of Motorcycle Maintenance 罗伯特-皮尔希，《禅与摩托车维护的艺术
Introduction: The System Lens 导言：系统透镜
Managers are not confronted with problems that are independent of each other, but with dynamic situations that consist of complex systems of changing problems that interact with each other. I call such situations messes. . . . Managers do not solve problems, they manage messes. 管理者面临的问题并不是相互独立的，而是由不断变化的问题组成的复杂系统相互作用的动态局面。我把这种情况称为 "混乱"。. . .管理者不是解决问题，而是管理混乱。
Early on in teaching about systems, I often bring out a Slinky. In case you grew up without one, a Slinky is a toy-a long, loose spring that can be made to bounce up and down, or pour back and forth from hand to hand, or walk itself downstairs. 在系统教学的初期，我经常会拿出一个弹簧球。如果你从小到大都没有玩过，那么 "弹簧狗 "就是一种玩具--一种长长的、松散的弹簧，它可以上下跳动，也可以在手中来回弹动，还可以自己走下楼去。
I perch the Slinky on one upturned palm. With the fingers of the other hand, I grasp it from the top, partway down its coils. Then I pull the bottom hand away. The lower end of the Slinky drops, bounces back up again, yo-yos up and down, suspended from my fingers above. 我把弹簧狗放在一只手掌上。我用另一只手的手指从上往下抓住它的线圈。然后我把下面的手拉开。链球的下端掉了下来，又弹了回去，上下晃动，悬挂在我的手指上。
"What made the Slinky bounce up and down like that?" I ask students. "是什么让弹簧狗这样上下跳动？"我问学生。
"Your hand. You took away your hand," they say. "你的手你拿走了你的手，"他们说。
So I pick up the box the Slinky came in and hold it the same way, poised on a flattened palm, held from above by the fingers of the other hand. With as much dramatic flourish as I can muster, I pull the lower hand away. 于是，我拿起装有弹簧狗的盒子，用同样的方法把它放在扁平的手掌上，用另一只手的手指从上面握住。我用我所能表现出的最夸张的手法，把下面那只手拉了开来。
Nothing happens. The box just hangs there, of course. 什么也没发生。当然，盒子只是挂在那里。
"Now once again. What made the Slinky bounce up and down?" "现在再来一次是什么让弹簧狗上下跳动？"
The answer clearly lies within the Slinky itself. The hands that manipulate it suppress or release some behavior that is latent within the structure of the spring. 答案显然就在弹弓本身。操纵它的双手会抑制或释放潜藏在弹簧结构中的某些行为。
That is a central insight of systems theory. 这是系统理论的核心观点。
Once we see the relationship between structure and behavior, we can begin to understand how systems work, what makes them produce poor results, and how to shift them into better behavior patterns. As our world 一旦我们看清了结构与行为之间的关系，我们就能开始理解系统是如何运作的，是什么让它们产生了糟糕的结果，以及如何将它们转变为更好的行为模式。当我们的世界
continues to change rapidly and become more complex, systems thinking will help us manage, adapt, and see the wide range of choices we have before us. It is a way of thinking that gives us the freedom to identify root causes of problems and see new opportunities. 随着全球环境的不断快速变化和日趋复杂，系统思维将帮助我们管理、适应和洞察摆在我们面前的各种选择。这种思维方式让我们能够自由地找出问题的根源，看到新的机遇。
So, what is a system? A system is a set of things-people, cells, molecules, or whatever-interconnected in such a way that they produce their own pattern of behavior over time. The system may be buffeted, constricted, triggered, or driven by outside forces. But the system's response to these forces is characteristic of itself, and that response is seldom simple in the real world. 那么，什么是系统呢？系统是一组事物--人、细胞、分子或其他任何东西--相互连接在一起，随着时间的推移产生自己的行为模式。系统可能受到外力的冲击、限制、触发或驱动。但系统对这些力量的反应是其自身的特征，而这种反应在现实世界中很少是简单的。
When it comes to Slinkies, this idea is easy enough to understand. When it comes to individuals, companies, cities, or economies, it can be heretical. The system, to a large extent, causes its own behavior! An outside event may unleash that behavior, but the same outside event applied to a different system is likely to produce a different result. 说到 "弹弓"，这种想法很容易理解。但如果涉及到个人、公司、城市或经济，这可能就是异端邪说了。在很大程度上，系统是自身行为的根源！外部事件可能会引发这种行为，但同样的外部事件应用到不同的系统中，很可能会产生不同的结果。
Think for a moment about the implications of that idea: 请想一想这个想法的含义：
Political leaders don't cause recessions or economic booms. Ups and downs are inherent in the structure of the market economy. 政治领导人不会导致经济衰退或经济繁荣。经济起伏是市场经济结构所固有的。
Competitors rarely cause a company to lose market share. They may be there to scoop up the advantage, but the losing company creates its losses at least in part through its own business policies. 竞争对手很少导致公司失去市场份额。它们可能会抢走优势，但失去市场份额的公司至少有一部分是通过自身的商业政策造成的。
The oil-exporting nations are not solely responsible for oilprice rises. Their actions alone could not trigger global price rises and economic chaos if the oil consumption, pricing, and investment policies of the oil-importing nations had not built economies that are vulnerable to supply interruptions. 石油出口国并不是石油价格上涨的唯一责任者。如果石油进口国的石油消费、定价和投资政策没有建立起易受供应中断影响的经济，仅靠它们的行动是不可能引发全球价格上涨和经济混乱的。
The flu virus does not attack you; you set up the conditions for it to flourish within you. 流感病毒不会攻击你，而是你为它在你体内滋生创造了条件。
Drug addiction is not the failing of an individual and no one person, no matter how tough, no matter how loving, can cure a drug addict—not even the addict. It is only through understanding addiction as part of a larger set of influences and societal issues that one can begin to address it. 吸毒成瘾不是个人的过失，没有一个人，无论多么坚强，无论多么有爱心，能够治愈吸毒成瘾者，甚至连吸毒成瘾者自己都做不到。只有将毒瘾理解为一系列更大的影响因素和社会问题的一部分，才能着手解决它。
Something about statements like these is deeply unsettling. Something else is purest common sense. I submit that those two somethings-a resistance to and a recognition of systems principles-come from two kinds of human experience, both of which are familiar to everyone. 诸如此类的言论让人深感不安。另一些东西则是最纯粹的常识。我认为，这两种东西--对系统原则的抵制和对系统原则的认可--来自于两种人类经验，而这两种经验对每个人来说都是熟悉的。
On the one hand, we have been taught to analyze, to use our rational ability, to trace direct paths from cause to effect, to look at things in small and understandable pieces, to solve problems by acting on or controlling the world around us. That training, the source of much personal and societal power, leads us to see presidents and competitors, OPEC and the flu and drugs as the causes of our problems. 一方面，我们被教导要善于分析，要运用我们的理性能力，从原因到结果直接追踪路径，把事情看成一个个可以理解的小片段，通过采取行动或控制我们周围的世界来解决问题。这种训练是个人和社会力量的源泉，它让我们把总统和竞争对手、欧佩克、流感和毒品视为问题的根源。
On the other hand, long before we were educated in rational analysis, we all dealt with complex systems. We are complex systems-our own bodies are magnificent examples of integrated, interconnected, self-maintaining complexity. Every person we encounter, every organization, every animal, garden, tree, and forest is a complex system. We have built up intuitively, without analysis, often without words, a practical understanding of how these systems work, and how to work with them. 另一方面，早在我们接受理性分析教育之前，我们都在与复杂系统打交道。我们就是复杂系统--我们自己的身体就是综合、相互关联、自我维护的复杂性的杰出典范。我们遇到的每个人、每个组织、每只动物、花园、树木和森林都是一个复杂系统。对于这些系统如何运作，以及如何与它们合作，我们已经建立了直观的、无需分析的、往往是无需言语的实际理解。
Modern systems theory, bound up with computers and equations, hides the fact that it traffics in truths known at some level by everyone. It is often possible, therefore, to make a direct translation from systems jargon to traditional wisdom. 现代系统理论与计算机和方程式紧密相连，掩盖了它所蕴含的人人皆知的真理。因此，通常可以将系统术语直接转化为传统智慧。
Because of feedback delays within complex systems, by the time a problem becomes apparent it may be unnecessarily difficult to solve. 由于复杂系统中存在反馈延迟，当问题显现时，解决起来可能已经非常困难。
A stitch in time saves nine. 一针可以救九命。
According to the competitive exclusion principle, if a reinforcing feedback loop rewards the winner of a competition with the means to win further competitions, the result will be the elimination of all but a few competitors. 根据竞争排斥原理，如果一个强化反馈回路向竞争获胜者提供赢得更多竞争的手段，其结果将是除少数竞争者外的所有竞争者都被淘汰。
For he that hath, to him shall be given; and he that hath not, from him shall be taken even that which he hath (Mark 4:25) or 因为有的，要赐给他；没有的，连他所有的也要夺过来（马可福音 4：25）或
-The rich get richer and the poor get poorer. -富人更富，穷人更穷。
A diverse system with multiple pathways and redundancies is 一个具有多种途径和冗余的多样化系统是
more stable and less vulnerable to external shock than a uniform system with little diversity. 与缺乏多样性的统一系统相比，它更稳定，更不易受到外部冲击的影响。
Don't put all your eggs in one basket. 不要把所有鸡蛋都放在一个篮子里。
Ever since the Industrial Revolution, Western society has benefited from science, logic, and reductionism over intuition and holism. Psychologically and politically we would much rather assume that the cause of a problem is "out there," rather than "in here." It's almost irresistible to blame something or someone else, to shift responsibility away from ourselves, and to look for the control knob, the product, the pill, the technical fix that will make a problem go away. 自工业革命以来，西方社会一直受益于科学、逻辑和还原论，而非直觉和整体论。在心理上和政治上，我们更愿意假设问题的原因在 "外面"，而不是 "这里"。将问题归咎于某物或他人，将责任从自己身上转移开，寻找能让问题消失的控制钮、产品、药片和技术解决方案，这几乎是不可抗拒的。
Serious problems have been solved by focusing on external agentspreventing smallpox, increasing food production, moving large weights and many people rapidly over long distances. Because they are embedded in larger systems, however, some of our "solutions" have created further problems. And some problems, those most rooted in the internal structure of complex systems, the real messes, have refused to go away. 通过对外部因素的关注，一些严重的问题已经得到了解决，如预防天花、提高粮食产量、长距离快速移动重物和人员等。然而，由于这些问题蕴含在更大的系统中，我们的一些 "解决方案 "造成了更多的问题。而有些问题，那些最根植于复杂系统内部结构的问题，那些真正的混乱，却一直不肯消失。
Hunger, poverty, environmental degradation, economic instability, unemployment, chronic disease, drug addiction, and war, for example, persist in spite of the analytical ability and technical brilliance that have been directed toward eradicating them. No one deliberately creates those problems, no one wants them to persist, but they persist nonetheless. That is because they are intrinsically systems problems-undesirable behaviors characteristic of the system structures that produce them. They will yield only as we reclaim our intuition, stop casting blame, see the system as the source of its own problems, and find the courage and wisdom to restructure it. 例如，饥饿、贫困、环境退化、经济不稳定、失业、慢性疾病、吸毒和战争，尽管人们已经通过分析能力和技术才华消除了这些问题，但它们依然存在。没有人刻意制造这些问题，也没有人希望它们持续存在，但它们依然存在。这是因为它们本质上是系统问题--产生这些问题的系统结构所特有的不良行为。只有当我们重拾直觉，停止指责，将系统视为自身问题的根源，并找到重组系统的勇气和智慧时，它们才会屈服。
Obvious. Yet subversive. An old way of seeing. Yet somehow new. Comforting, in that the solutions are in our hands. Disturbing, because we must do things, or at least see things and think about things, in a different way. 显而易见。但却具有颠覆性。古老的观察方式。但又有新意。令人欣慰的是，解决方案掌握在我们手中。令人不安，因为我们必须以不同的方式做事，或至少以不同的方式看待问题和思考问题。
This book is about that different way of seeing and thinking. It is intended for people who may be wary of the word "systems" and the field of systems analysis, even though they may have been doing systems thinking all their lives. I have kept the discussion nontechnical because I want to show what a long way you can go toward understanding systems without turning to mathematics or computers. 本书讲述的就是这种不同的观察和思考方式。本书的读者可能对 "系统 "一词和系统分析领域心存戒备，尽管他们可能一生都在进行系统思考。我之所以保持非技术性的讨论，是因为我想向读者展示，不借助数学或计算机，你也可以在理解系统方面走得很远。
I have made liberal use of diagrams and time graphs in this book 我在本书中大量使用了图表和时间曲线图
because there is a problem in discussing systems only with words. Words and sentences must, by necessity, come only one at a time in linear, logical order. Systems happen all at once. They are connected not just in one direction, but in many directions simultaneously. To discuss them properly, it is necessary somehow to use a language that shares some of the same properties as the phenomena under discussion. 因为只用词语来讨论系统是有问题的。词语和句子必须按照线性逻辑顺序一个一个地出现。系统是同时发生的。它们不仅在一个方向上，而且在多个方向上同时发生联系。要正确地讨论它们，就必须以某种方式使用一种与所讨论的现象具有某些相同特性的语言。
Pictures work for this language better than words, because you can see all the parts of a picture at once. I will build up systems pictures gradually, starting with very simple ones. I think you'll find that you can understand this graphical language easily. 图片比文字更适合这种语言，因为你可以同时看到图片的所有部分。我将从非常简单的图片开始，逐步建立图片系统。我想你会发现，你可以很容易地理解这种图形语言。
I start with the basics: the definition of a system and a dissection of its parts (in a reductionist, unholistic way). Then I put the parts back together to show how they interconnect to make the basic operating unit of a system: the feedback loop. 我从最基本的开始：系统的定义和各部分的剖析（以还原论和非整体论的方式）。然后，我把各个部分重新组合在一起，展示它们是如何相互连接以构成系统的基本运行单元：反馈回路。
Next I will introduce you to a systems zoo-a collection of some common and interesting types of systems. You'll see how a few of these creatures behave and why and where they can be found. You'll recognize them; they're all around you and even within you. 接下来，我将向你介绍一个系统动物园--一个由一些常见的、有趣的系统类型组成的集合。你将看到其中一些生物的行为方式和原因，以及在哪里可以找到它们。你一定能认出它们，它们就在你身边，甚至就在你体内。
With a few of the zoo "animals"—a set of specific examples-as a foundation, I'll step back and talk about how and why systems work so beautifully and the reasons why they so often surprise and confound us. I'll talk about why everyone or everything in a system can act dutifully and rationally, yet all these well-meaning actions too often add up to a perfectly terrible result. And why things so often happen much faster or slower than everyone thinks they will. And why you can be doing something that has always worked and suddenly discover, to your great disappointment, that your action no longer works. And why a system might suddenly, and without warning, jump into a kind of behavior you've never seen before. 有了动物园里的几种 "动物"--一组具体的例子--作为基础，我将退后一步，谈谈系统是如何以及为什么能如此完美地运作，以及它们常常让我们感到惊讶和困惑的原因。我将谈谈为什么系统中的每个人或每件事都能尽职尽责、理性行事，但所有这些善意的行为却往往会导致非常糟糕的结果。为什么事情发生的速度往往比每个人想象的要快得多或慢得多。为什么你在做一件一直有效的事情时，会突然失望地发现你的行动不再有效了？还有，为什么一个系统会在毫无征兆的情况下，突然出现一种你从未见过的行为。
That discussion will lead to us to look at the common problems that the systems-thinking community has stumbled upon over and over again through working in corporations and governments, economies and ecosystems, physiology and psychology. "There's another case of the tragedy of the commons," we find ourselves saying as we look at an allocation system for sharing water resource among communities or financial resources among schools. Or we identify "eroding goals" as we study the business rules and incentives that help or hinder the development of new technologies. Or we see "policy resistance" as we examine decision-making power and the nature of relationships in a 这一讨论将引导我们审视系统思考界在企业和政府、经济和生态系统、生理学和心理学等领域工作时一再发现的共同问题。"当我们研究社区间共享水资源或学校间共享财政资源的分配制度时，我们发现自己在说："这又是一个公地悲剧的案例。或者，当我们研究有助于或阻碍新技术发展的商业规则和激励措施时，我们会发现 "目标正在被侵蚀"。或者，当我们研究决策权和关系性质时，我们会看到 "政策阻力"。
family, a community, or a nation. Or we witness "addiction"—which can be caused by many more agents than caffeine, alcohol, nicotine, and narcotics. 家庭、社区或国家。或者，我们目睹了 "成瘾"--除了咖啡因、酒精、尼古丁和毒品之外，还有许多其他物质也会导致成瘾。
Systems thinkers call these common structures that produce characteristic behaviors "archetypes." When I first planned this book, I called them "system traps." Then I added the words "and opportunities," because these archetypes, which are responsible for some of the most intransigent and potentially dangerous problems, also can be transformed, with a little systems understanding, to produce much more desirable behaviors. 系统思想家把这些产生特征行为的常见结构称为 "原型"。在我最初策划本书时，我称它们为 "系统陷阱"。后来我又加上了 "和机遇 "几个字，因为这些原型造成了一些最顽固、最具潜在危险性的问题，但只要对系统稍加了解，它们也可以转变，产生更理想的行为。
From this understanding I move into what you and I can do about restructuring the systems we live within. We can learn how to look for leverage points for change. 从这一认识出发，我开始探讨你我可以做些什么来重构我们所处的系统。我们可以学习如何寻找变革的杠杆点。
I conclude with the largest lessons of all, the ones derived from the wisdom shared by most systems thinkers I know. For those who want to explore systems thinking further, the Appendix provides ways to dig deeper into the subject with a glossary, a bibliography of systems thinking resources, a summary list of systems principles, and equations for the models described in Part One. 最后，我将从我所认识的大多数系统思考者的智慧中总结出最重要的经验。对于那些想进一步探索系统思维的人，附录中的词汇表、系统思维资源书目、系统原理汇总表以及第一部分中描述的模型方程，为深入研究这一主题提供了方法。
When our small research group moved from MIT to Dartmouth College years ago, one of the Dartmouth engineering professors watched us in seminars for a while, and then dropped by our offices. "You people are different," he said. "You ask different kinds of questions. You see things I don't see. Somehow you come at the world in a different way. How? Why?" 多年前，当我们的小型研究小组从麻省理工学院搬到达特茅斯学院时，达特茅斯学院的一位工程学教授观看了我们的研讨会，然后顺便去了我们的办公室。"他说："你们与众不同。他说，"你们问的问题与众不同。你们看到了我看不到的东西。不知怎的，你们以一种不同的方式来看待这个世界。怎么不同？为什么？"
That's what I hope to get across throughout this book, but especially in its conclusion. I don't think the systems way of seeing is better than the reductionist way of thinking. I think it's complementary, and therefore revealing. You can see some things through the lens of the human eye, other things through the lens of a microscope, others through the lens of a telescope, and still others through the lens of systems theory. Everything seen through each kind of lens is actually there. Each way of seeing allows our knowledge of the wondrous world in which we live to become a little more complete. 这就是我希望在本书中，尤其是在结论部分所要表达的意思。我并不认为系统观察法比简化思维法更好。我认为它是互补的，因此具有启发性。你可以通过人眼的视角来观察某些事物，通过显微镜的视角来观察其他事物，通过望远镜的视角来观察其他事物，通过系统理论的视角来观察其他事物。通过每一种透镜看到的事物其实都是存在的。每一种观察方式都能让我们对我们生活的这个奇妙世界的认识变得更加完整。
At a time when the world is more messy, more crowded, more interconnected, more interdependent, and more rapidly changing than ever before, the more ways of seeing, the better. The systems-thinking lens allows us to reclaim our intuition about whole systems and - see interconnections 当今世界比以往任何时候都更加混乱、更加拥挤、更加相互关联、更加相互依存、变化更加迅速，因此，看待世界的方法越多越好。系统思维的视角让我们重新找回对整个系统的直觉，并看到相互联系
- ask "what-if" questions about possible future behaviors, and - 就未来可能出现的行为提出 "假设 "问题，以及
- be creative and courageous about system redesign. - 勇于创新，大胆进行系统重新设计。
Then we can use our insights to make a difference in ourselves and our world. 然后，我们就可以利用我们的洞察力来改变我们自己和我们的世界。
INTERLUDE The Blind Men and the Matter of the Elephant 间奏曲 《盲人摸象记
Beyond Ghor, there was a city. All its inhabitants were blind. A king with his entourage arrived nearby; he brought his army and camped in the desert. He had a mighty elephant, which he used to increase the people's awe. 在古尔之外，有一座城市。城里的居民都是盲人。一位国王带着他的随从来到了附近；他带着他的军队，在沙漠中安营扎寨。他有一头强大的大象，用来增加人们的敬畏之心。
The populace became anxious to see the elephant, and some sightless from among this blind community ran like fools to find it. 人们急切地想看到大象，盲人群体中的一些盲人像傻子一样跑去寻找大象。
As they did not even know the form or shape of the elephant, they groped sightlessly, gathering information by touching some part of it. 由于他们甚至不知道大象的形态和形状，他们只能盲目地摸索，通过触摸大象的某个部位来收集信息。
Each thought that he knew something, because he could feel a part.... The man whose hand had reached an ear . . . said: "It is a large, rough thing, wide and broad, like a rug." 每个人都以为自己知道些什么，因为他能感觉到一部分....那个手伸向耳朵的人说"这是一个又大又粗糙的东西 又宽又阔，就像一块地毯"
And the one who had felt the trunk said: "I have the real facts about it. It is like a straight and hollow pipe, awful and destructive." 那个摸到箱子的人说："我知道它的真实情况它就像一根又直又空的管子，可怕而具有破坏性。"
The one who had felt its feet and legs said: "It is mighty and firm, like a pillar." 摸过它腿脚的人说"它强大而坚固，就像一根柱子"
Each had felt one part out of many. Each had perceived it wrongly. ... This ancient Sufi story was told to teach a simple lesson but one that we often ignore: The behavior of a system cannot be known just by knowing the elements of which the system is made. 每个人都感受到了其中的一部分。每个人都有错误的认识。... 讲述这个古老的苏菲故事是为了给我们上一堂简单的课，但我们却常常忽略了这一课：仅仅了解构成系统的元素是无法知道系统的行为的。
The Basics 基础知识
I have yet to see any problem, however complicated, which, when looked at in the right way, did not become still more complicated. 我还没有见过任何问题，无论多么复杂，只要用正确的方法去研究，就不会变得更加复杂。
一Poul Anderson 一 普尔-安德森
More Than the Sum of Its Parts 超越各部分的总和
A system isn't just any old collection of things. A system is an interconnected set of elements that is coherently organized in a way that achieves something. If you look at that definition closely for a minute, you can see that a system must consist of three kinds of things: elements, interconnections, and a function or purpose. 系统并不只是各种事物的旧集合。一个系统 是一组相互关联的元素，它们以某种方式连贯地组织起来，从而达到某种目的。如果你仔细研究一下这个定义，就会发现一个系统必须由三种东西组成：元素、相互联系以及功能或目的。
For example, the elements of your digestive system include teeth, enzymes, stomach, and intestines. They are interrelated through the physi flow of food, and through an elegant set of regulating chemical signals. The function of this system is to break down food into its basic nutrients and to transfer those nutrients into the bloodstream (another system), while discarding unusable wastes. 例如，消化系统的要素包括牙齿、酶、胃和肠。它们通过生理 食物流和一套优雅的化学调节信号相互关联。这个系统的功能是将食物分解成基本的营养物质，并将这些营养物质输送到血液中（另一个系统），同时丢弃无法使用的废物。
A football team is a system with elements such as players, coach, field, and ball. Its interconnections are the rules of the game, the coach's strategy, the players' communications, and the laws of physics that govern the motions of ball and players. The purpose of the team is to win games, or have fun, or get exercise, or make millions of dollars, or all of the above. 足球队是一个由球员、教练、场地和球等要素组成的系统。它的相互联系是比赛规则、教练的策略、球员的交流，以及支配球和球员运动的物理定律。球队的目的是赢得比赛，或获得乐趣，或锻炼身体，或赚取数百万美元，或以上所有目的。
A school is a system. So is a city, and a factory, and a corporation, and a national economy. An animal is a system. A tree is a system, and a forest is a larger system that encompasses subsystems of trees and animals. The earth is a system. So is the solar system; so is a galaxy. Systems can be embedded in systems, which are embedded in yet other systems. 学校是一个系统。城市、工厂、公司和国家经济也是如此。动物是一个系统。一棵树是一个系统，而一片森林则是一个更大的系统，其中包括树木和动物的子系统。地球是一个系统。太阳系也是一个系统，银河系也是一个系统。系统可以嵌入系统，而系统又嵌入其他系统。
Is there anything that is not a system? Yes-a conglomeration without any particular interconnections or function. Sand scattered on a road by happenstance is not, itself, a system. You can add sand or take away sand and you still have just sand on the road. Arbitrarily add or take away football players, or pieces of your digestive system, and you quickly no longer have the same system. 有什么东西不是一个系统吗？有--一个没有任何特定的相互联系或功能的集合体。偶然散落在路上的沙子本身并不是一个系统。你可以添加沙子，也可以拿走沙子，但路上仍然只有沙子。任意添加或移除足球运动员或消化系统的碎片，你很快就不再拥有相同的系统了。
When a living creature dies, it loses its "system-ness." The multiple interrelations that held it together no longer function, and it dissipates, although its material remains part of a larger 当生物死亡时，它就失去了 "系统性"。维系它的多重相互关系不再起作用，它也随之消散，尽管它的物质仍是更大系统的一部分。
A system is more than the sum of its parts. It may exhibit adaptive, dynamic, goal-seking, self-preserving, and sometimes evolutionary behavior. food-web system. Some people say that an old city neighborhood where people know each other and communicate regularly is a social system, and that a new apartment block full of strangers is not-not until new relationships arise and a system forms. 系统不仅仅是各部分的总和。它可能表现出适应性的、动态的、追求目标的、自我保护的行为，有时甚至是进化行为。有人说，在一个城市的老社区里，人们相互认识并经常交流，这就是一个社会系统；而在一个新的公寓区里，到处都是陌生人，这就不是一个社会系统--直到出现新的关系并形成一个系统。
You can see from these examples that there is an integrity or wholeness about a system and an active set of mechanisms to maintain that integrity. Systems can change, adapt, respond to events, seek goals, mend injuries, and attend to their own survival in lifelike ways, although they may contain or consist of nonliving things. Systems can be self-organizing, and often are self-repairing over at least some range of disruptions. They are resilient, and many of them are evolutionary. Out of one system other completely new, never-beforeimagined systems can arise. 从这些例子中可以看出，系统具有完整性或整体性，并有一套积极的机制来维持这种完整性。系统可以改变、适应、应对事件、寻求目标、修补损伤，并以栩栩如生的方式关注自身的生存，尽管它们可能包含或由非生物组成。系统可以自我组织，通常至少在一定范围的干扰下可以自我修复。它们具有复原力，其中许多是进化而来的。从一个系统中可以产生其他全新的、前所未见的系统。
Look Beyond the Players to the Rules of the Game 跳出球员看游戏规则
You think that because you understand "one" that you must therefore understand "two" because one and one make two. But you forget that you must also understand "and." 你以为理解了 "一"，就一定能理解 "二"，因为一加一等于二。但你忘了，你还必须理解 "和"。
-Sufi teaching story -苏菲教学故事
The elements of a system are often the easiest parts to notice, because many of them are visible, tangible things. The elements that make up a tree are roots, trunk, branches, and leaves. If you look more closely, you 一个系统的要素往往是最容易被注意到的部分，因为其中很多都是看得见、摸得着的东西。构成一棵树的要素有树根、树干、树枝和树叶。如果仔细观察，你会发现
THINK ABOUT THIS 想想看
How to know whether you are looking at a system or just a bunch of stuff: 如何知道你看到的是一个系统还是一堆东西：
A) Can you identify parts? . . . and A) 你能识别零件吗？......和
B) Do the parts affect each other? . . . and B) 各部分是否相互影响？......以及
C) Do the parts together produce an effect that is different from the effect of each part on its own? ... and perhaps C)各部分共同产生的效果是否不同于各部分单独产生的效果？......或许
D) Does the effect, the behavior over time, persist in a variety of circumstances? D) 随着时间的推移，这种效果和行为是否会在各种情况下持续存在？
see specialized cells: vessels carrying fluids up and down, chloroplasts, and so on. The system called a university is made up of buildings, students, professors, administrators, libraries, books, computers-and I could go on and say what all those things are made up of. Elements do not have to be physical things. Intangibles are also elements of a system. In a university, school pride and academic prowess are two intangibles that can be very important elements of the system. Once you start listing the elements of a system, there is almost no end to the process. You can divide elements into sub-elements and then sub-sub-elements. Pretty soon you lose sight of the system. As the saying goes, you can't see the forest for the trees. 我们可以看到专门的细胞：上下输送液体的血管、叶绿体等等。被称为大学的系统由建筑、学生、教授、管理人员、图书馆、书籍、计算机组成--我还可以继续说这些东西是由什么组成的。要素不一定是有形的东西。无形资产也是一个系统的要素。在一所大学中，学校荣誉和学术实力就是两种无形的东西，它们可能是系统中非常重要的元素。一旦开始列出一个系统的要素，这个过程就几乎没有尽头。你可以把要素分为子要素，然后再分为子要素。很快，你就会忽略整个系统。正所谓 "只见树木，不见森林"。
Before going too far in that direction, it's a good idea to stop dissecting out elements and to start looking for the interconnections, the relationships that hold the elements together. 在朝着这个方向走得太远之前，最好先停止对元素的剖析，开始寻找元素之间的相互联系和关系。
The interconnections in the tree system are the physical flows and chemical reactions that govern the tree's metabolic processes-the signals that allow one part to respond to what is happening in another part. For example, as the leaves lose water on a sunny day, a drop in pressure in the water-carrying vessels allows the roots to take in more water. Conversely, if the roots experience dry soil, the loss of water pressure signals the leaves to close their pores, so as not to lose even more precious water. 树木系统中的相互联系是指支配树木新陈代谢过程的物理流动和化学反应，也就是让一个部分对另一个部分发生的情况做出反应的信号。例如，当树叶在晴天失水时，运水血管中的压力下降会让树根吸收更多水分。反之，如果根部遇到干燥的土壤，水压的下降就会向叶片发出信号，使其关闭毛孔，以免失去更多宝贵的水分。
As the days get shorter in the temperate zones, a deciduous tree puts forth chemical messages that cause nutrients to migrate out of the leaves into the trunk and roots and that weaken the stems, allowing the leaves to 在温带地区，随着白昼变短，落叶树会发出化学信息，使养分从树叶中转移到树干和树根中，从而削弱茎干，使树叶能够在短时间内生长。
fall. There even seem to be messages that cause some trees to make repellent chemicals or harder cell walls if just one part of the plant is attacked by insects. No one understands all the relationships that allow a tree to do what it does. That lack of knowledge is not surprising. It's easier to learn about a system's elements than about its interconnections. 秋天。如果植物的某一部分受到昆虫的攻击，一些树木甚至会发出信息，制造驱虫化学物质或制造更坚硬的细胞壁。没有人了解树木之所以能够生长的所有关系。缺乏知识并不奇怪。了解一个系统的要素比了解其相互联系要容易得多。
In the university system, interconnections include the standards for admission, the requirements for degrees, the examinations and grades, the budgets and money flows, the gossip, and most important, the communication of knowledge that is, presumably, the purpose of the whole system. 在大学系统中，相互联系包括入学标准、学位要求、考试和成绩、预算和资金流动、流言蜚语，以及最重要的知识传播，这大概是整个系统的目的。
Some interconnections in systems are actual physi- 系统中的某些相互联系是实际的物理联系。
Many of the interconnections in systems operate through the flow of information. Information holds systems together and plays a great role in determining how they operate. cal flows, such as the water in the tree's trunk or the students progressing through a university. Many interconnections are flows of information-signals that go to decision points or action points within a system. These kinds of interconnections are often harder to see, but the system reveals them to those who look. Students may use informal information about the probability of getting a good grade to decide what courses to take. A consumer decides what to buy using information about his or her income, savings, credit rating, stock of goods at home, prices, and availability of goods for purchase. Governments need information about kinds and quantities of water pollution before they can create sensible regulations to reduce that pollution. (Note that information about the existence of a problem may be necessary but not sufficient to trigger action-information about resources, incentives, and consequences is necessary too.) 系统中的许多相互联系都是通过信息流来实现的。信息流，如树干中的水流或大学中的学生流。许多互联都是信息流--通往系统内决策点或行动点的信号。这些相互联系通常较难察觉，但系统会向观察者揭示它们。学生可能会利用关于取得好成绩概率的非正式信息来决定选修什么课程。消费者会利用有关其收入、储蓄、信用等级、家中商品存量、价格和可购买商品的信息来决定购买什么。政府需要有关水污染种类和数量的信息，然后才能制定合理的法规来减少污染。(请注意，关于问题存在的信息可能是必要的，但不足以引发行动--关于资源、激励措施和后果的信息也是必要的）。
If information-based relationships are hard to see, functions or purposes are even harder. A system's function or purpose is not necessarily spoken, written, or expressed explicitly, except through the operation of the system. The best way to deduce the system's purpose is to watch for a while to see how the system behaves. 如果说基于信息的关系难以察觉，那么功能或目的就更加难以察觉。一个系统的功能或目的并不一定是通过语言、文字或明确表达出来的，除非通过系统的运行。推断系统目的的最好办法就是观察一段时间，看看系统是如何运行的。
If a frog turns right and catches a fly, and then turns left and catches a fly, and then turns around backward and catches a fly, the purpose of the frog has to do not with turning left or right or backward but with catching flies. If a government proclaims its interest in protecting the environment but allocates little money or effort toward that goal, environmental protection is not, in fact, the government's purpose. Purposes are deduced from behavior, not from rhetoric or stated goals. 如果一只青蛙向右转抓住了一只苍蝇，向左转又抓住了一只苍蝇，向后转又抓住了一只苍蝇，那么青蛙的目的就不是向左转、向右转或向后转，而是抓住苍蝇。如果一个政府宣称它有兴趣保护环境，但却很少为这一目标投入资金或精力，那么环境保护事实上并不是政府的目的。目的是从行为中推导出来的，而不是从夸夸其谈或宣称的目标中推导出来的。
A NOTE ON LANGUAGE 关于语言的说明
The word function is generally used for a nonhuman system, the word purpose for a human one, but the distinction is not absolute, since so many systems have both human and nonhuman elements. 功能一词通常用于非人类系统，目的一词用于人类系统，但这种区分并不是绝对的，因为有许多系统既有人类元素，也有非人类元素。
The function of a thermostat-furnace system is to keep a building at a given temperature. One function of a plant is to bear seeds and create more plants. One purpose of a national economy is, judging from its behavior, to keep growing larger. An important function of almost every system is to ensure its own perpetuation. 恒温器-壁炉系统的功能是使建筑物保持一定的温度。植物的功能之一是结出种子，创造更多的植物。从国民经济的行为来看，其目的之一就是不断壮大。几乎所有系统的一个重要功能都是确保自身的永续发展。
System purposes need not be human purposes and are not necessarily those intended by any single actor within the system. In fact, one of the most frustrating aspects of systems is that the purposes of subunits may add up to an overall behavior that no one wants. No one intends to produce a society with rampant drug addiction and crime, but consider the combined purposes and consequent actions of the actors involved: 系统的目的不一定是人类的目的，也不一定是系统中任何一个参与者的目的。事实上，系统最令人沮丧的一点是，子单元的目的可能会导致无人想要的整体行为。没有人想制造一个吸毒和犯罪猖獗的社会，但请考虑一下相关行为者的综合目的和随之而来的行动：
desperate people who want quick relief from psychological pain 希望快速缓解心理痛苦的绝望者
farmers, dealers, and bankers who want to earn money 想赚钱的农民、商人和银行家
pushers who are less bound by civil law than are the police who oppose them 他们比反对他们的警察更不受民法约束
governments that make harmful substances illegal and use police power to interdict them 政府将有害物质定为非法，并利用警察权力加以拦截
wealthy people living in close proximity to poor people 富人与穷人为邻
nonaddicts who are more interested in protecting themselves than in encouraging recovery of addicts 非瘾君子对保护自己比鼓励瘾君子戒毒更感兴趣
Altogether, these make up a system from which it is extremely difficult to eradicate drug addiction and crime. 这些因素共同构成了一个极难根除吸毒和犯罪的系统。
Systems can be nested within systems. Therefore, there can be purposes within purposes. The purpose of a university is to discover and preserve knowledge and pass it on to new generations. Within the university, the purpose of a student may be to get good grades, the purpose of a professor 系统中可以嵌套系统。因此，目的之中也可以有目的。大学的目的是发现和保存知识，并将其传承给下一代。在大学内部，学生的目的可能是取得好成绩，教授的目的可能是
may be to get tenure, the purpose of an administrator may be to balance the budget. Any of those sub-purposes could come into conflict with the overall purpose-the student could cheat, the professor could ignore the students in order to publish papers, the administrator could balance the budget by firing professors. Keeping sub-purposes and overall system purposes in harmony is an essential function of successful systems. I'll get back to this point later when we come to hierarchies. 学生的目的可能是获得终身教职，管理者的目的可能是平衡预算。这些子目的中的任何一个都可能与总体目的发生冲突--学生可能会作弊，教授可能会为了发表论文而忽视学生，管理者可能会通过解雇教授来平衡预算。保持子目的与系统整体目的的和谐是成功系统的基本功能。稍后，当我们谈到等级制度时，我会回到这一点。
You can understand the relative importance of a system's elements, interconnections, and purposes by imagining them changed one by one. Changing elements usually has the least effect on the system. If you change all the players on a football team, it is still recognizably a football team. (It may play much better or much worse-particular elements in a system can indeed be important.) A tree changes its cells constantly, its leaves every year or so, but it is still essentially the same tree. Your body replaces most of its cells every few weeks, but it goes on being your body. The university has a constant flow of students and a slower flow of professors and administrators, but it is still a university. In fact it is still the same university, distinct in subtle ways from others, just as General Motors and the U.S. Congress somehow maintain their identities even though all their members change. A system generally goes on being itself, changing only slowly if at all, even with complete substitutions of its elements-as long as its interconnections and purposes remain intact. 通过想象系统中的元素、相互联系和目的逐一改变，您就能了解它们的相对重要性。改变元素通常对系统的影响最小。如果把一支足球队的所有球员都换掉，它仍然是一支足球队。(它可能踢得更好，也可能踢得更差--系统中的特定元素可能确实很重要）。一棵树会不断更换细胞，每隔一年左右就会更换树叶，但它本质上仍然是同一棵树。你的身体每隔几周就会更换大部分细胞，但它仍然是你的身体。大学里的学生源源不断，教授和管理人员流动较慢，但它仍然是一所大学。事实上，它仍然是同一所大学，只是以微妙的方式区别于其他大学，就像通用汽车公司和美国国会在所有成员都发生变化的情况下，仍然以某种方式保持着自己的身份一样。一般来说，只要系统的相互联系和目的保持不变，系统就会一直存在下去，即使其要素完全替换，也只是缓慢地发生变化。
If the interconnections change, the system may be greatly altered. It may even become unrecognizable, even though the same players are on the team. Change the rules from those of football to those of basketball, and you've got, as they say, a whole new ball game. If you change the interconnections in the tree-say that instead of taking in carbon dioxide and emitting oxygen, it does the reverse-it would no longer be a tree. (It would be an animal.) If in a university the students graded the professors, or if arguments were won by force instead of reason, the place would need a different name. It might be an interesting organization, but it would not be a university. Changing interconnections in a system can change it dramatically. 如果相互联系发生变化，系统可能会发生巨大变化。甚至可能变得面目全非，即使球队中的球员还是那些球员。把足球规则改成篮球规则，就像人们说的那样，你会得到一个全新的球赛。如果你改变了树的相互联系--比如说，它不再吸收二氧化碳和释放氧气，而是反过来--它就不再是一棵树了（它将成为一种动物）。 如果在大学里，学生给教授打分，或者如果争论是以武力而不是理性取胜，那么这个地方就需要一个不同的名字。它可能是一个有趣的组织，但不会是一所大学。改变一个系统中的相互联系可以使其发生巨大变化。
Changes in function or purpose also can be drastic. What if you keep the players and the rules but change the purpose-from winning to losing, for example? What if the function of a tree were not to survive and repro- 功能或目的的改变也可能是急剧的。如果保留球员和规则，但改变目的--比如从赢球到输球--会怎样？如果一棵树的功能不再是生存和繁衍，那又会怎样？
duce but to capture all the nutrients in the soil and grow to unlimited size? People have imagined many purposes for a university besides disseminating knowledge-making money, indoctrinating people, winning football games. A change in purpose changes a system profoundly, even if every element and interconnection remains the same. 除了汲取土壤中的所有养分，大学还能无限大吗？除了传播知识--赚钱、灌输思想、赢得足球比赛之外，人们还为大学设想了许多目的。目的的改变会深刻地改变一个系统，即使每个元素和相互联系保持不变。
To ask whether elements, interconnections, or purposes are most important in a system is to ask an unsystemic question. All are essential. All interact. All have their roles. But the least obvious part of the system, its function or purpose, is often the most crucial determinant of the system's behavior. Interconnections are also critically important. Changing relationships usually changes system behavior. The elements, the parts of systems we are most likely to notice, are often (not always) least important in defining the unique characteristics of the system-unless changing an element also results in changing relationships or purpose. 要问一个系统中最重要的是元素、相互联系还是目的，这是个非系统问题。所有要素都是必不可少的。所有元素都相互作用。都有各自的作用。但系统中最不明显的部分，即系统的功能或目的，往往是决定系统行为的最关键因素。相互联系也至关重要。改变关系通常会改变系统行为。我们最有可能注意到的系统元素，往往（并非总是）是决定系统独特特征的最不重要因素--除非改变某个元素也会导致系统关系或目的的改变。
Changing just one leader at the top-from a Brezhnev to a Gorbachev, or from a Carter to a Reagan-may or may not turn an entire nation in a new direction, though its land, factories, and hundreds of millions of people remain exactly the same. A leader can make that land and those factories and people play a different game with new rules, or can direct the play toward a new purpose. 仅仅更换一位最高领导人--从勃列日涅夫到戈尔巴乔夫，或从卡特到里根--可能会也可能不会将整个国家带向一个新的方向，尽管其土地、工厂和数亿人口仍然完全相同。领导人可以让这片土地、这些工厂和人民用新的规则玩不同的游戏，也可以把游戏引向新的目的。
And conversely, because land, factories, and people are long-lived, slowly changing, physical elements of the system, there is a limit to the rate at which any leader can turn the direction of a nation. 反过来说，由于土地、工厂和人口是系统中长期存在、缓慢变化的物理要素，任何领导者扭转国家方向的速度都是有限的。
Bathtubs 101-Understanding System Behavior over Time 浴缸 101--了解系统随时间变化的行为
Information contained in nature ... allows us a partial reconstruction of the past.... The development of the meanders in a river, the increasing complexity of the earth's crust . . . are information-storing devices in the same manner that genetic systems are.... Storing information means increasing the complexity of the mechanism. 大自然中蕴含的信息......让我们能够部分重建过去....河流的蜿蜒发展、地壳的日益复杂......都是储存信息的装置，就像基因系统一样....。存储信息意味着增加机制的复杂性。
-Ramon Margalef -拉蒙-马尔加莱夫
A stock is the foundation of any system. Stocks are the elements of the system that you can see, feel, count, or measure at any given time. A system stock is just what it sounds like: a store, a quantity, an accumulation of 股票是任何系统的基础。库存是系统中你可以随时看到、感觉到、数到或测量到的元素。系统库存就像它的名字一样：一个仓库、一个数量、一个累积的
material or information that has built up over time. It may be the water in a bathtub, a population, the books in a bookstore, the wood in a tree, the money in a bank, your own self-confidence. A stock does not have to be physical. Your reserve of good will toward others 长期积累的材料或信息。它可以是浴缸里的水，可以是人口，可以是书店里的书，可以是树上的木头，可以是银行里的钱，也可以是你自己的自信。储备不一定是有形的。你对他人的善意储备
A stock is the memory of the history of changing flows within the system. or your supply of hope that the world can be better are both stocks. 存量是对系统内流动变化历史的记忆。
Stocks change over time through the actions of a flow. Flows are filling and draining, births and deaths, purchases and sales, growth and decay, deposits and withdrawals, successes and failures. A stock, then, is the present memory of the history of changing flows within the system. 股票随着时间的推移在流动中发生变化。流动包括填充和流失、出生和死亡、购买和销售、增长和衰减、存款和取款、成功和失败。那么，存量就是系统内流动变化历史的当前记忆。
Figure 1. How to read stock-and-flow diagrams. In this book, stocks are shown as boxes, and flows as arrow-headed "pipes" leading into or out of the stocks. The small T on each flow signifies a "faucet;" it can be turned higher or lower, on or off. The "clouds" stand for wherever the flows come from and go to-the sources and sinks that are being ignored for the purposes of the present discussion. 图 1.如何阅读存量与流量图。在本书中，股票以方框表示，资金流则以带箭头的 "管道 "表示，流入或流出股票。每个流量上的小 T 代表一个 "水龙头"，可以调高或调低，打开或关闭。云 "代表流量的来源和去向，也就是本文讨论中忽略的源和汇。
For example, an underground mineral deposit is a stock, out of which comes a flow of ore through mining. The inflow of ore into a mineral deposit is minute in any time period less than eons. So I have chosen to draw (Figure 2) a simplified picture of the system without any inflow. All system diagrams and descriptions are simplified versions of the real world. 例如，地下矿藏是一个存量，通过开采，矿石从这里流出。在任何时间段内，矿石流入矿床的量都是微乎其微的。因此，我选择绘制一幅没有矿石流入的简化系统图（图 2）。所有系统图和描述都是现实世界的简化版。
Figure 2. A stock of minerals depleted by mining. 图 2.因采矿而枯竭的矿物库存。
Water in a reservoir behind a dam is a stock, into which flow rain and river water, and out of which flows evaporation from the reservoir's surface as well as the water discharged through the dam. 大坝后水库中的水是一种蓄水，雨水和河水流入水库，水库表面的蒸发水以及通过大坝排出的水从水库中流出。
Figure 3. A stock of water in a reservoir with multiple inflows and outflows. 图 3.水库中的水量，有多个流入和流出口。
The volume of wood in the living trees in a forest is a stock. Its inflow is the growth of the trees. Its outflows are the natural deaths of trees and the harvest by loggers. The logging harvest flows into another stock, perhaps an inventory of lumber at a mill. Wood flows out of the inventory stock as lumber sold to customers. 森林中活树的木量是一种存量。它的流入量是树木的生长量。流出量是树木的自然死亡和伐木工人的采伐。伐木收获的木材流入另一个库存，也许是木材厂的木材库存。木材从库存中流出，成为出售给客户的木材。
Figure 4. A stock of lumber linked to a stock of trees in a forest. 图 4.木材库存与森林中的树木库存相关联。
If you understand the dynamics of stocks and flows-their behavior over time-you understand a good deal about the behavior of complex systems. And if you have had much experience with a bathtub, you understand the dynamics of stocks and flows. 如果你了解存量和流量的动态--它们随时间变化的行为--你就能很好地理解复杂系统的行为。如果你有过很多使用浴缸的经验，你就会理解存量和流量的动态变化。
Figure 5. The structure of a bathtub system-one stock with one inflow and one outflow. 图 5 浴缸系统的结构浴缸系统的结构--一个存量，一个流入，一个流出。
Imagine a bathtub filled with water, with its drain plugged up and its faucets turned off-an unchanging, undynamic, boring system. Now 想象一下，一个装满水的浴缸，下水道被堵住，水龙头被关闭--一个一成不变、没有活力、枯燥乏味的系统。现在
mentally pull the plug. The water runs out, of course. The level of water in the tub goes down until the tub is empty. 精神上拔掉插头。水当然会流出来。浴缸里的水位一直在下降，直到浴缸里的水被抽空。
Figure 6. Water level in a tub when the plug is pulled. 图 6.拔出塞子时浴缸中的水位。
A NOTE ON READING GRAPHS OF BEHAVIOR OVER TIME 阅读行为随时间变化的图表的注意事项
Systems thinkers use graphs of system behavior to understand trends over time, rather than focusing attention on individual events. We also use behavior-over-time graphs to learn whether the system is approaching a goal or a limit, and if so, how quickly. The variable on the graph may be a stock or a flow. The pattern-the shape of the variable line-is important, as are the points at which that line changes shape or direction. The precise numbers on the axes are often less important. 系统思想家使用系统行为图来了解一段时间内的趋势，而不是将注意力集中在单个事件上。我们还利用行为随时间变化图来了解系统是否正在接近目标或极限，如果是，接近的速度有多快。图中的变量可以是存量或流量。模式--变量线的形状--很重要，线的形状或方向发生变化的点也很重要。坐标轴上的精确数字通常不那么重要。
The horizontal axis of time allows you to ask questions about what came before, and what might happen next. It can help you focus on the time horizon appropriate to the question or problem you are investigating. 时间横轴可以让你对之前发生的事情和接下来可能发生的事情提出问题。它可以帮助你将注意力集中在与你正在研究的问题相适应的时间范围上。
Now imagine starting again with a full tub, and again open the drain, but this time, when the tub is about half empty, turn on the inflow faucet so the rate of water flowing in is just equal to that flowing out. What happens? 现在想象一下，在浴缸满水的情况下，再次打开下水道，但这一次，当浴缸大约空了一半时，打开进水龙头，使流入的水量与流出的水量相等。会发生什么？
The amount of water in the tub stays constant at whatever level it had reached when the inflow became equal to the outflow. It is in a state of dynamic equilibrium-its level does not change, although water is continuously flowing through it. 当流入的水量等于流出的水量时，浴缸中的水量保持不变。它处于动态平衡状态--虽然水不断流过，但水位不会改变。
Figure 7. Constant outflow, inflow turned on after 5 minutes, and the resulting changes in the stock of water in the tub. 图 7.恒定流出，5 分钟后开启流入，以及由此导致的浴缸中水存量的变化。
Imagine turning the inflow on somewhat harder while keeping the outflow constant. The level of water in the tub slowly rises. If you then turn the inflow 想象一下，在保持流出量不变的情况下，稍稍加大流入量。浴缸中的水位会慢慢上升。如果您再将流入量
faucet down again to match the outflow exactly, the water in the tub will stop rising. Turn it down some more, and the water level will fall slowly. 再将水龙头关小，使其与流出的水完全吻合，浴缸中的水就会停止上升。再把水龙头调小一些，水位就会慢慢下降。
This model of a bathtub is a very simple system with just one stock, one inflow, and one outflow. Over the time period of interest (minutes), I have assumed that evaporation from the tub is insignificant, so I have not included that outflow. All models, whether mental models or mathematical models, are simplifications of the real world. You know all the dynamic possibilities of this bathtub. From it you can deduce several important principles that extend to more complicated systems: 这个浴缸模型是一个非常简单的系统，只有一个存量、一个流入量和一个流出量。在所关注的时间段内（分钟），我假设浴缸的蒸发量很小，因此没有将流出量包括在内。所有模型，无论是心理模型还是数学模型，都是对真实世界的简化。你知道这个浴缸的所有动态可能性。从中你可以推导出一些重要的原理，这些原理可以延伸到更复杂的系统中：
As long as the sum of all inflows exceeds the sum of all outflows, the level of the stock will rise. 只要所有流入量的总和超过所有流出量的总和，存量水平就会上升。
As long as the sum of all outflows exceeds the sum of all inflows, the level of the stock will fall. 只要所有流出量的总和超过所有流入量的总和，存量水平就会下降。
If the sum of all outflows equals the sum of all inflows, the stock level will not change; it will be held in dynamic equilibrium at whatever level it happened to be when the two sets of flows became equal. 如果所有流出量的总和等于所有流入量的总和，那么存量水平就不会发生变化；它将保持在动态平衡状态，即两组流量相等时的水平。
The human mind seems to focus more easily on stocks than on flows. On top of that, when we do focus on flows, we tend to focus on inflows more easily than on outflows. Therefore, we sometimes miss seeing that we can fill a bathtub not only by increasing the inflow rate, 人的大脑似乎更容易关注股票，而不是流量。此外，当我们关注流量时，我们往往更容易关注流入，而不是流出。因此，我们有时会忽略这样一个事实，即我们不仅可以通过增加流入量来填满浴缸，还可以通过增加流出量来填满浴缸、
A stock can be increased by decreasing its outflow rate as well as by increasing its inflow rate. There's more than one way to fill a bathtub! but also by decreasing the outflow rate. Everyone understands that you can prolong the life of an oilbased economy by discovering new oil deposits. It seems to be harder to understand that the same result can be achieved by burning less oil. A breakthrough in energy efficiency is equivalent, in its effect on the stock of available oil, to the discovery of a new oil field—although different people profit from it. 减少流出量和增加流入量都可以增加存量。装满浴缸的方法不止一种！但也可以通过降低流出率来实现。每个人都明白，通过发现新的石油矿藏，可以延长以石油为基础的经济的寿命。但似乎更难理解的是，减少石油燃烧也能达到同样的效果。能源效率的突破对石油存量的影响相当于发现了新油田，尽管从中获利的人不同。
Similarly, a company can build up a larger workforce by more hiring, or it can do the same thing by reducing the rates of quitting and firing. These two strategies may have very different costs. The wealth of a nation can be boosted by investment to build up a larger stock of factories and machines. It also can be boosted, often more cheaply, by decreasing the rate at which factories and machines wear out, break down, or are discarded. 同样，公司可以通过增加招聘来扩大员工队伍，也可以通过降低辞职率和解雇率来达到同样的目的。这两种策略的成本可能截然不同。一个国家的财富可以通过投资来增加工厂和机器的数量。通过降低工厂和机器的磨损、损坏或废弃速度，也可以增加财富，而且往往成本更低。
You can adjust the drain or faucet of a bathtub-the flows-abruptly, but it is much more difficult to change the level of water-the stockquickly. Water can't run out the drain instantly, even if you open the drain all the way. The tub can't fill up immediately, even with the inflow faucet on full blast. A stock takes time to change, because flows take time to flow. That's a vital point, a key to understanding why systems behave as they do. Stocks usually change slowly. They can act as delays, lags, buffers, ballast, and sources of momentum in a system. Stocks, especially large ones, respond to change, even sudden change, only by gradual filling or emptying. 您可以随意调节浴缸的下水道或水龙头--水流，但要快速改变水位--存水量则要困难得多。即使将排水口全部打开，水也不会立即从排水口流出。即使将进水龙头开到最大，浴缸也不可能立即注满水。股价的变化需要时间，因为水流的流动需要时间。这是至关重要的一点，也是理解系统为何如此的关键所在。存量通常变化缓慢。它们可以作为系统中的延迟、滞后、缓冲、压舱物和动力源。存量，尤其是大型存量，只能通过逐渐填充或清空的方式来应对变化，甚至是突如其来的变化。
People often underestimate the inherent momentum of a stock. It takes a long time for populations to grow or stop growing, for wood Stocks generally change to accumulate in a forest, for a reservoir to fill up, slowly, even when the flows into or out of them change suddenly. Therefore, stocks act as delays or buffers or shock absorbers in systems. for a mine to be depleted. An economy cannot build up a large stock of functioning factories and highways and electric plants overnight, even if a lot of money is available. Once an economy has a lot of oil-burning furnaces and automobile engines, it cannot change quickly to furnaces and engines that burn a different fuel, even if the price of oil suddenly changes. It has taken decades to accumulate the stratospheric pollutants that destroy the earth's ozone layer; it will take decades for those pollutants to be removed. 人们往往低估了种群的内在动力。人口增长或停止增长需要很长时间，森林中的木材需要很长时间，水库需要很长时间才能慢慢蓄满，即使流入或流出水库的水流发生了突然的变化。因此，库存在系统中起着延迟、缓冲或减震的作用。即使有大量资金，一个经济体也不可能在一夜之间建立起大量运转正常的工厂、高速公路和发电厂。一旦一个经济体拥有了大量燃烧石油的熔炉和汽车发动机，即使石油价格突然发生变化，它也无法迅速改用燃烧其他燃料的熔炉和发动机。破坏地球臭氧层的平流层污染物积累了几十年，要清除这些污染物也需要几十年的时间。
Changes in stocks set the pace of the dynamics of systems. Industrialization cannot proceed faster than the rate at which factories and machines can be constructed and the rate at which human beings can be educated to run and maintain them. Forests can't grow overnight. Once contaminants have accumulated in groundwater, they can be washed out only at the rate of groundwater turnover, which may take decades or even centuries. 存量的变化决定了系统动态的速度。工业化的发展速度不可能快于建造工厂和机器的速度，也不可能快于教育人类来运行和维护这些机器的速度。森林不可能在一夜之间生长。污染物一旦积聚在地下水中，就只能以地下水周转的速度被冲走，而这可能需要几十年甚至几百年的时间。
The time lags that come from slowly changing stocks can cause problems in systems, but they also can be sources of stability. Soil that has accumulated over centuries rarely erodes all at once. A population that has learned many skills doesn't forget them immediately. You can pump groundwater faster than the rate it recharges for a long time before the aquifer is drawn down far enough to be damaged. The time lags imposed by stocks allow room to maneuver, to experiment, and to revise policies that aren't working. 缓慢变化的存量所带来的时滞会给系统带来问题，但也可能成为稳定的源泉。积累了几个世纪的土壤很少会一下子被侵蚀。学会了许多技能的人不会马上忘记这些技能。在地下蓄水层被抽取到足以被破坏之前，你可以以比它的补给速度更快的速度抽取地下水很长时间。股票所带来的时间滞后性使我们有余地进行操作、试验，并对行不通的政策进行修改。
If you have a sense of the rates of change of stocks, you don't expect things to happen faster than they can happen. You don't give up too soon. 如果你对股票的变化率有所了解，你就不会期望事情发生得比它们可能发生的更快。你不会过早放弃。
You can use the opportunities presented by a system's momentum to guide it toward a good outcome-much as a judo expert uses the momentum of an opponent to achieve his or her own goals. 你可以利用系统的动力所带来的机会，引导它取得好的结果--就像柔道高手利用对手的动力来实现自己的目标一样。
There is one more important principle about the role of stocks in systems, a principle that will lead us directly to the concept of feedback. The presence of stocks allows inflows and outflows to be 关于存量在系统中的作用，还有一个重要的原则，这个原则将直接引导我们找到反馈的概念。存量的存在可以让流入和流出
Stocks allow inflows and outflows to be decoupled and to be independent and temporarily out of balance with each other. independent of each other and temporarily out of balance with each other. 股票允许流入和流出脱钩，相互独立，暂时失去平衡。
It would be hard to run an oil company if gasoline had to be produced at the refinery at exactly the rate the cars were burning it. It isn't feasible to harvest a forest at the precise rate at which the trees are growing. Gasoline in storage tanks and wood in the forest are both stocks that permit life to proceed with some certainty, continuity, and predictability, even though flows vary in the short term. 如果炼油厂生产汽油的速度必须与汽车燃烧汽油的速度完全一致，那么石油公司就很难经营下去。以树木生长的精确速度采伐森林也是不可行的。储油罐中的汽油和森林中的木材都是存量，即使短期内流量会发生变化，但它们都能使生活在一定程度上具有确定性、连续性和可预测性。
Human beings have invented hundreds of stock-maintaining mechanisms to make inflows and outflows independent and stable. Reservoirs enable residents and farmers downriver to live without constantly adjusting their lives and work to a river's varying flow, especially its droughts and floods. Banks enable you temporarily to earn money at a rate different from how you spend. Inventories of products along a chain from distributors to wholesalers to retailers allow production to proceed smoothly although customer demand varies, and allow customer demand to be filled even though production rates vary. 人类发明了数以百计的蓄水机制，使流入和流出保持独立和稳定。水库使下游的居民和农民无需根据河流的流量变化，特别是干旱和洪水的变化，不断调整自己的生活和工作。银行能让你暂时以不同于消费方式的利率赚钱。从分销商到批发商再到零售商的产业链上的产品库存，使生产能够顺利进行，尽管客户的需求各不相同，并使客户的需求能够在生产率不同的情况下得到满足。
Most individual and institutional decisions are designed to regulate the levels in stocks. If inventories rise too high, then prices are cut or advertising budgets are increased, so that sales will go up and inventories will fall. If the stock of food in your kitchen gets low, you go to the store. As the stock of growing grain rises or fails to rise in the fields, farmers decide whether to apply water or pesticide, grain companies decide how many barges to book for the harvest, speculators bid on future values of the harvest, cattle growers build up or cut down their herds. Water levels in reservoirs cause all sorts of corrective actions if they rise too high or fall too low. The same can be said for the stock of money in your wallet, the oil reserves owned by an oil company, the pile of woodchips feeding a paper mill, and the concentration of pollutants in a lake. 大多数个人和机构的决策都是为了调节库存水平。如果库存过高，就会降价或增加广告预算，这样销售额就会上升，库存就会下降。如果厨房里的食物存量不足，你就会去商店购买。随着田间谷物存量的增加或减少，农民会决定是用水还是施用杀虫剂，谷物公司会决定为收成预订多少驳船，投机者会对收成的未来价值进行竞价，养牛者会增加或减少牛群数量。水库的水位如果升得过高或降得过低，就会引起各种纠正措施。钱包里的钱的存量、石油公司拥有的石油储备、造纸厂的木屑堆以及湖泊中污染物的浓度也是如此。
People monitor stocks constantly and make decisions and take actions 人们不断监测库存，并做出决定和采取行动
designed to raise or lower stocks or to keep them within acceptable ranges. Those decisions add up to the ebbs and flows, successes and problems, of all sorts of systems. Systems thinkers see the world as a collection of stocks along with the mechanisms for regulating the levels in the stocks by manipulating flows. 这些决定的目的是提高或降低存量，或将其保持在可接受的范围内。这些决定导致了各种系统的起伏、成功和问题。在系统思想家眼中，世界是一个种群的集合体，同时还有通过控制流量来调节种群水平的机制。
That means system thinkers see the world as a collection of "feedback processes." 这意味着系统思想家将世界视为 "反馈过程 "的集合。
How the System Runs Itself-Feedback 系统如何自我运行--反馈
Systems of information-feedback control are fundamental to all life and human endeavor, from the slow pace of biological evolution to the launching of the latest space satellite. . . . Everything we do as individuals, as an industry, or as a society is done in the context of an information-feedback system. 从缓慢的生物进化到发射最新的太空卫星，信息反馈控制系统是所有生命和人类活动的基础。. . .作为个人、行业或社会，我们所做的一切都离不开信息反馈系统。
— —ay W. Forrester -ay W. Forrester
When a stock grows by leaps and bounds or declines swiftly or is held within a certain range no matter what else is going on around it, it is likely that there is a control mechanism at work. In other words, if you see a behavior that persists over time, there is likely a mechanism creating that consistent behavior. That mechanism operates through a feedback loop. It is the consistent behavior pattern over a long period of time that is the first hint of the existence of a feedback loop. 当一只股票的涨幅突飞猛进，或跌幅迅猛，或无论周围发生了什么，都保持在一定的范围内时，很可能是有一种控制机制在起作用。换句话说，如果你看到一种行为长期存在，那么很可能有一种机制在创造这种一致的行为。这种机制是通过反馈回路运行的。长期持续的行为模式是反馈回路存在的第一个暗示。
A feedback loop is formed when changes in a stock affect the flows into or out of that same stock. A feedback loop can be quite simple and direct. Think of an interest-bearing savings account in a bank. The total amount of money in the account (the stock) affects how much money comes into the account as interest. That is because the bank has a rule that the account earns a certain percent interest each year. The total dollars of interest paid into the account each year (the flow in) is not a fixed amount, but varies with the size of the total in the account. 当某一存量的变化影响到同一存量的流入或流出时，就形成了反馈回路。反馈回路可以非常简单和直接。想想银行里的一个计息储蓄账户。账户中的资金总额（存量）会影响到有多少资金作为利息进入账户。这是因为银行规定该账户每年可获得一定百分比的利息。每年支付到账户中的利息总额（流入量）并不是一个固定的数额，而是随着账户总额的变化而变化。
You experience another fairly direct kind of feedback loop when you get your bank statement for your checking account each month. As your level of available cash in the checking account (a stock) goes down, you may decide to work more hours and earn more money. The money entering 当你每月拿到支票账户的银行对账单时，你会经历另一种相当直接的反馈回路。当支票账户中的可用现金（股票）水平下降时，你可能会决定增加工作时间，赚更多的钱。进入
your bank account is a flow that you can adjust in order to increase your stock of cash to a more desirable level. If your bank account then grows very large, you may feel free to work less (decreasing the inflow). This kind of feedback loop is keeping your level of cash available within a range that is acceptable to you. You can see that adjusting your earnings is not the only feedback loop that works on your stock of cash. You also may be able to adjust the outflow of money from your account, for example. You can imagine an outflow-adjusting feedback loop for spending. 您的银行账户是您可以调整的流量，以便将您的现金存量增加到更理想的水平。如果你的银行账户变得很大，你就可以减少工作（减少流入）。这种反馈循环使你的可用现金水平保持在你可以接受的范围内。由此可见，调整收入并不是影响现金存量的唯一反馈回路。例如，你还可以调整账户的资金流出量。你可以想象一个调整支出的反馈回路。
Feedback loops can cause stocks to maintain their level within a range or grow or decline. In any case, the flows into or out of the stock are adjusted because of changes in the size of the stock itself. Whoever or whatever is monitoring the stock's level begins a corrective process, adjusting rates of inflow or outflow (or both) and so changing the stock's level. The stock level feeds back through a chain of signals and actions to control itself. 反馈回路可导致存量在一定范围内保持水平，或增长或下降。在任何情况下，流入或流出存量都会因存量本身规模的变化而有所调整。监测股票水平的人或机构会开始一个纠正过程，调整流入或流出的速度（或两者），从而改变股票水平。存量水平通过一连串的信号和行动进行反馈，以控制自身。
Figure 8. How to read a stock-and-flow diagram with feedback loops. Each diagram distinguishes the stock, the flow that changes the stock, and the information link (shown as a thin, curved arrow) that directs the action. It emphasizes that action or change always proceeds through adjusting flows. 图 8.如何阅读带有反馈回路的存量与流量图。每个图都区分了存量、改变存量的流程以及指导行动的信息链接（以细长的弯曲箭头表示）。它强调了行动或变化总是通过调整流程进行的。
Not all systems have feedback loops. Some systems are relatively simple open-ended chains of stocks and flows. The chain may be affected by outside factors, but the levels of the chain's stocks don't affect its flows. However, those systems that contain feedback loops are common and may be quite elegant or rather surprising, as we shall see. 并非所有系统都有反馈回路。有些系统是相对简单的存量和流量的开放式链条。该链可能会受到外界因素的影响，但链中存量的高低并不影响其流量。然而，那些包含反馈回路的系统很常见，而且可能相当优雅，也可能相当惊人，我们将拭目以待。
A feedback loop is a closed chain of causal connections from a stock, through a set of decisions or rules or physical laws or actions that are dependent on the level of the stock, and back again through a flow to change the stock. 反馈回路是一个封闭的因果联系链，它从一个存量出发，通过一系列依赖于存量水平的决策、规则或物理定律或行动，再通过改变存量的流程返回。
Stabilizing Loops-Balancing Feedback 稳定环路-平衡反馈
One common kind of feedback loop stabilizes the stock level, as in the checking-account example. The stock level may not remain completely fixed, but it does stay within an acceptable range. What follows are some more stabilizing feedback loops that may be familiar to you. These examples start to detail some of the steps within a feedback loop. 一种常见的反馈回路是稳定库存水平，如支票账户的例子。存货水平可能不会完全固定，但会保持在一个可接受的范围内。下面是一些大家可能比较熟悉的稳定反馈回路。这些例子开始详细说明反馈回路中的一些步骤。
If you're a coffee drinker, when you feel your energy level run low, you may grab a cup of hot black stuff to perk you up again. You, as the coffee drinker, hold in your mind a desired stock level (energy for work). The purpose of this caffeine-delivery system is to keep your actual stock level near or at your desired level. (You may have other purposes for drinking coffee as well: enjoying the flavor or engaging in a social activity.) It is the 如果你喜欢喝咖啡，当你感到精力不足时，你可能会喝上一杯热腾腾的黑咖啡，让自己重新振作起来。作为喝咖啡的人，你会在脑海中设定一个理想的能量水平（工作时的能量）。这种咖啡因输送系统的目的就是让你的实际存量接近或达到你所期望的水平。(你喝咖啡可能还有其他目的：享受咖啡的味道或参与社交活动）。它是
Figure 9. Energy level of a coffee drinker. 图 9喝咖啡者的能量水平。
gap, the discrepancy, between your actual and desired levels of energy for work that drives your decisions to adjust your daily caffeine intake. 您的实际工作精力水平与期望精力水平之间的差距，促使您决定调整每天的咖啡因摄入量。
Notice that the labels in Figure 9, like all the diagram labels in this book, are direction-free. The label says "stored energy in body" not "low energy level," “coffee intake" not "more coffee." That's because feedback loops often can operate in two directions. In this case, the feedback loop can correct an oversupply as well as an undersupply. If you drink too much coffee and find yourself bouncing around with extra energy, you'll lay off the caffeine for a while. High energy creates a discrepancy that says "too much," which then causes you to reduce your coffee intake until your energy level settles down. The diagram is intended to show that the loop works to drive the stock of energy in either direction. 请注意，图 9 中的标签和本书中的所有图表标签一样，是没有方向性的。标签上写的是 "体内储存的能量"，而不是 "能量水平低"；是 "咖啡摄入量"，而不是 "更多的咖啡"。这是因为反馈回路通常可以双向运行。在这种情况下，反馈回路既可以纠正供过于求，也可以纠正供不应求。如果你喝了太多咖啡，发现自己精力充沛，就会暂时停止摄入咖啡因。高能量会产生 "过多 "的差异，从而导致您减少咖啡摄入量，直到能量水平稳定下来。该图旨在说明，这个循环的作用是推动能量存量向任一方向变化。
I could have shown the inflow of energy coming from a cloud, but instead I made the system diagram slightly more complicated. Remember-all system diagrams are simplifications of the real world. We each choose how much complexity to look at. In this example, I drew another stock-the stored energy in the body that can be activated by the caffeine. I did that to indicate that there is more to the system than one simple loop. As every coffee drinker knows, caffeine is only a short-term stimulant. It lets you run your motor faster, but it doesn't refill your personal fuel tank. Eventually the caffeine high wears off, leaving the body more energy-deficient than it was before. That drop could reactivate the feedback loop and generate another trip to the coffee pot. (See the discussion of addiction later in this book.) Or it could activate some longer-term and healthier feedback responses: Eat some food, take a walk, get some sleep. 我本可以展示来自云层的能量流入，但我却让系统图变得稍微复杂了一些。请记住，所有系统图都是对现实世界的简化。我们每个人都可以选择看多复杂。在这个例子中，我画了另一个存量--体内储存的能量可以被咖啡因激活。我这样做是为了说明，这个系统不仅仅是一个简单的循环。每个喝咖啡的人都知道，咖啡因只是一种短期兴奋剂。它能让你的发动机运转得更快，但并不能补充你的个人油箱。最终，咖啡因的兴奋会逐渐消失，使身体比以前更缺乏能量。这一下降可能会重新激活反馈回路，让你再次去咖啡壶那里（见本书后面关于成瘾的讨论）：吃点东西、散散步、睡一觉。
This kind of stabilizing, goal-seeking, regulating loop is called a balancing feedback loop, so I put a B inside the loop in the diagram. Balancing feedback loops are goal-seeking or stability-seeking. Each tries to keep a stock at a given value or within a range of values. A balancing feedback loop opposes whatever direction of change is imposed on the system. If you push a stock too far up, a balancing loop will try to pull it back down. If you shove it too far down, a balancing loop will try to bring it back up. 这种稳定的、追求目标的调节回路被称为平衡反馈回路，所以我在图中的回路内加了一个 B。平衡反馈回路追求目标或稳定。每个反馈回路都试图将存量保持在给定值或一定范围内。平衡反馈回路反对强加给系统的任何变化方向。如果将股价推得过高，平衡反馈回路就会试图将其拉回来。如果将其推得太低，平衡反馈回路会试图将其拉回来。
Here's another balancing feedback loop that involves coffee, but one that works through physical law rather than human decision. A hot cup of coffee will gradually cool down to room temperature. Its rate of cooling depends on the difference between the temperature of the coffee and the temperature of the room. The greater the difference, the faster the coffee 这里还有一个涉及咖啡的平衡反馈回路，但它是通过物理规律而非人为决定发挥作用的。一杯热咖啡会逐渐冷却到室温。它的冷却速度取决于咖啡温度和室温之间的差异。温差越大，咖啡冷却的速度越快
will cool. The loop works the other way too-if you make iced coffee on a hot day, it will warm up until it has the same temperature as the room. The function of this system is to bring the discrepancy between coffee's temperature and room's temperature to zero, no matter what the direction of the discrepancy. 就会冷却。这个循环也可以反过来起作用--如果你在大热天煮冰咖啡，它就会升温，直到与室温相同。这个系统的功能就是将咖啡温度和室温之间的差异归零，无论差异的方向如何。
Figure 10. A cup of coffee cooling (left) or warming (right). 图 10一杯冷却（左）或加热（右）的咖啡。
Starting with coffee at different temperatures, from just below boiling to just above freezing, the graphs in Figure 11 show what will happen to the temperature over time (if you don't drink the coffee). You can see here the "homing" behavior of a balancing feedback loop. Whatever the initial value of the system stock (coffee temperature in this case), whether it is above or below the "goal" (room temperature), the feedback loop brings it toward 图 11 显示了温度随时间变化的情况（如果您不喝咖啡）。在这里，您可以看到平衡反馈回路的 "归位 "行为。无论系统存量（本例中为咖啡温度）的初始值是多少，也无论它是高于还是低于 "目标"（室温），反馈回路都会将其带向 "目标"。
Figure 11. Coffee temperature as it approaches a room temperature of . 图 11.咖啡在接近室温 时的温度。
the goal. The change is faster at first, and then slower, as the discrepancy between the stock and the goal decreases. 目标。随着存量与目标之间差距的减小，这种变化起初较快，随后逐渐减慢。
This behavior pattern-gradual approach to 这种循序渐进的行为模式
Balancingfeedbackloops are equilibrating or goal-seeking structures in systems and are both sources of stability and sources of resistance to change. a system-defined goal- also can be seen when a radioactive element decays, when a missile finds its target, when an asset depreciates, when a reservoir is brought up or down to its desired level, when your body adjusts its blood-sugar concentration, when you pull your car to a stop at a stoplight. You can think of many more examples. The world is full of goal-seeking feedback loops. 当放射性元素衰变时、当导弹发现目标时、当资产贬值时、当水库蓄水或蓄水量达到预期水平时、当你的身体调整血糖浓度时、当你把车停在红绿灯前时，都可以看到系统确定的目标。你还可以想到更多的例子。这个世界充满了追求目标的反馈回路。
The presence of a feedback mechanism doesn't necessarily mean that the mechanism works well. The feedback mechanism may not be strong enough to bring the stock to the desired level. Feedbacks-the interconnections, the information part of the system-can fail for many reasons. Information can arrive too late or at the wrong place. It can be unclear or incomplete or hard to interpret. The action it triggers may be too weak or delayed or resourceconstrained or simply ineffective. The goal of the feedback loop may never be reached by the actual stock. But in the simple example of a cup of coffee, the drink eventually will reach room temperature. 反馈机制的存在并不一定意味着该机制运行良好。反馈机制可能不够强大，无法使存量达到预期水平。反馈--系统中的相互联系和信息部分--失效的原因有很多。信息可能来得太晚，或者来错了地方。信息可能不清晰、不完整或难以解读。它所触发的行动可能过于微弱或延迟，或受到资源限制，或根本无效。实际存量可能永远达不到反馈回路的目标。但以一杯咖啡为例，咖啡最终会达到室温。
Runaway Loops-Reinforcing Feedback 失控循环-强化反馈
I'd need rest to refresh my brain, and to get rest it's necessary to travel, and to travel one must have money, and in order to get money you have to work. ...I am in a vicious circle ... from which it is impossible to escape. 我需要休息来提神醒脑，而要休息就必须旅行，要旅行就必须有钱，要有钱就必须工作。......我陷入了一个恶性循环......无法自拔。
—Honoré Balzac, 19th century novelist and playwright 19 世纪小说家和剧作家巴尔扎克
Here we meet a very important feature. It would seem as if this were circular reasoning; profits fell because investment fell, and investment fell because profits fell. 在这里，我们遇到了一个非常重要的特征。这似乎是一个循环论证：利润下降是因为投资下降，投资下降是因为利润下降。
—Jan Tinbergen, economist -Jan Tinbergen， 经济学家
The second kind of feedback loop is amplifying, reinforcing, self-multiplying, snowballing—a vicious or virtuous circle that can cause healthy growth 第二种反馈回路是放大、强化、自我倍增、滚雪球式的恶性循环或良性循环，可促进健康成长
or runaway destruction. It is called a reinforcing feedback loop, and will be noted with an in the diagrams. It generates more input to a stock the more that is already there (and less input the less that is already there). A reinforcing feedback loop enhances whatever direction of change is imposed on it. 或失控破坏。这就是所谓的强化反馈回路，在图中将用 标出。它使存量越多，投入就越多（存量越少，投入就越少）。强化反馈回路会增强任何方向的变化。
For example: 例如
When we were kids, the more my brother pushed me, the more I pushed him back, so the more he pushed me back, so the more I pushed him back. 小时候，哥哥越逼我，我就越逼他，他越逼我，我就越逼他。
The more prices go up, the more wages have to go up if people are to maintain their standards of living. The more wages go up, the more prices have to go up to maintain profits. This means that wages have to go up again, so prices go up again. 价格越是上涨，工资就越要上涨，这样才能维持人们的生活水平。工资涨得越多，价格就必须涨得越多，才能维持利润。这意味着工资必须再次上涨，因此物价再次上涨。
The more rabbits there are, the more rabbit parents there are to make baby rabbits. The more baby rabbits there are, the more grow up to become rabbit parents, to have even more baby rabbits. 兔子越多，就有越多的兔爸兔妈来制造兔宝宝。兔宝宝越多，就有越多的兔宝宝长大，成为兔父母，生出更多的兔宝宝。
The more soil is eroded from the land, the less plants are able to grow, so the fewer roots there are to hold the soil, so the more soil is eroded, so less plants can grow. 土地上的土壤被侵蚀得越多，植物的生长能力就越弱，因此用于固定土壤的根系就越少，土壤被侵蚀得越多，植物的生长能力就越弱。
The more I practice piano, the more pleasure I get from the sound, and so the more I play the piano, which gives me more practice. 我越是练习钢琴，就越能从琴声中获得愉悦，因此我弹得越多，练得也就越多。
Reinforcing loops are found wherever a system element has the ability to reproduce itself or to grow as a constant fraction of itself. Those elements include populations and economies. Remember the example of 只要系统元素有能力自我复制或作为自身的一个恒定部分不断增长，就会出现强化循环。这些元素包括人口和经济。还记得
Figure 12. Interest-bearing bank account. 图 12.计息银行账户。
the interest-bearing bank account? The more money you have in the bank, the more interest you earn, which is added to the money already in the bank, where it earns even more interest. 有利息的银行账户？银行里的钱越多，赚取的利息也就越多，这些利息会被加到已经存在银行里的钱上，从而赚取更多的利息。
Figure 13 shows how this reinforcing loop multiplies money, starting with in the bank, and assuming no deposits and no withdrawals over a period of twelve years. The five lines show five different interest rates, from 2 percent to 10 percent per year. 图 13 显示了这个强化循环是如何使资金成倍增长的，从银行中的 开始，假设在 12 年中没有存款也没有取款。五条线表示五种不同的利率，年利率从 2% 到 10%。
Figure 13. Growth in savings with various interest rates. 图 13.不同利率下的储蓄增长情况。
This is not simple linear growth. It is not constant over time. The growth of the bank account at lower interest rates may look linear in the first few years. But, in fact, growth goes faster and faster. The more is there, the more is added. This kind of growth is called "exponential." It's either good news or bad news, depending on what is growing-money in the bank, people 这不是简单的线性增长。它不是长期不变的。银行账户在较低利率下的增长在最初几年可能看起来是线性的。但实际上，增长速度越来越快。存在的越多，增加的就越多。这种增长被称为 "指数增长"。这要么是好消息，要么是坏消息，取决于增长的是什么--银行里的钱，人
Reinforcing feedback loops are self-enhancing, leading to exponential growth or to runaway collapses over time. They are found whenever a stock has the capacity to reinforce or reproduce itself. with HIV/AIDS, pests in a cornfield, a national economy, or weapons in an arms race. 强化反馈回路具有自我强化作用，随着时间的推移会导致指数式增长或失控崩溃。艾滋病毒/艾滋病、玉米田里的害虫、国民经济或军备竞赛中的武器都是如此。
In Figure 14, the more machines and factories (collectively called "capital") you have, the more goods and services ("output") you can produce. The more output you can produce, the more you can invest in new machines and factories. The more you make, the more capacity you have to make even more. This reinforcing feedback loop is the central engine of growth in an economy. 在图 14 中，拥有的机器和工厂（统称为 "资本"）越多，就能生产出越多的商品和服务（"产出"）。产出越多，投资新机器和新工厂的资金就越多。你生产的越多，你就有更大的能力去生产更多。这种不断强化的反馈循环是经济增长的核心动力。
Figure 14. Reinvestment in capital. 图 14.资本再投资。
By now you may be seeing how basic balancing and reinforcing feedback loops are to systems. Sometimes I challenge my students to try to think of any human decision that occurs without a feedback loop-that is, a decision that is made without regard to any information about the level of the stock it influences. Try thinking about that yourself. The more you do, the more you'll begin to see feedback loops everywhere. 现在你可能已经明白，平衡和强化反馈回路对于系统来说是多么基本。有时，我会挑战我的学生，让他们试着想一想，在没有反馈回路的情况下，人类会做出什么样的决定--也就是说，人类在做出决定时，并没有考虑到它所影响的存量水平的任何信息。试着自己思考一下。你想得越多，就会发现反馈回路无处不在。
The most common "non-feedback" decisions students suggest are falling in love and committing suicide. I'll leave it to you to decide whether you think these are actually decisions made with no feedback involved. 学生们提出的最常见的 "无反馈 "决定是恋爱和自杀。至于你是否认为这些决定实际上是在没有任何反馈的情况下做出的，那就留给你自己去判断吧。
Watch out! If you see feedback loops everywhere, you're already in danger of becoming a systems thinker! Instead of seeing only how A causes B, you'll begin to wonder how B may also influence A-and how A might reinforce or reverse itself. When you hear in the nightly news that the Federal Reserve 小心！如果你看到到处都是反馈回路，那么你就已经有成为系统思考者的危险了！你不会只看到 A 如何导致 B，而是会开始思考 B 如何影响 A，以及 A 如何强化或逆转自身。当你在晚间新闻中听到美联储
HINT ON REINFORCING LOOPS AND DOUBLING TIME 关于加强循环和加倍时间的提示
Because we bump into reinforcing loops so often, it is handy to know this shortcut: The time it takes for an exponentially growing stock to double in size, the "doubling time," equals approximately 70 divided by the growth rate (expressed as a percentage). 因为我们经常会遇到强化循环，所以知道这个捷径很方便：指数增长的股票规模翻倍所需的时间，即 "翻倍时间"，约等于 70 除以增长率（以百分比表示）。
Example: If you put in the bank at interest per year, you will double your money in 10 years . If you get only interest, your money will take 14 years to double. 举例说明：如果您把 存入银行，每年的利息为 ，那么您的钱将在 10 年后翻一番 。如果您只获得 利息，您的钱需要 14 年才能翻一番。
Bank has done something to control the economy, you'll also see that the economy must have done something to affect the Federal Reserve Bank. When someone tells you that population growth causes poverty, you'll ask yourself how poverty may cause population growth. 如果你认为联邦储备银行在控制经济方面做了什么，你也会认为经济一定做了什么来影响联邦储备银行。当有人告诉你人口增长导致贫困时，你会问自己贫困是如何导致人口增长的。
THINK ABOUT THIS: 想想看
If causes , is it possible that also causes ? 如果 会导致 ，那么 是否也会导致 呢？
You'll be thinking not in terms of a static world, but a dynamic one. You'll stop looking for who's to blame; instead you'll start asking, "What's the system?" The concept of feedback opens up the idea that a system can cause its own behavior. 你将不再从静态世界的角度思考问题，而是从动态世界的角度思考问题。你将不再追究责任，而是开始追问："系统是什么？"反馈 "的概念让我们认识到，系统可以导致自己的行为。
So far, I have limited this discussion to one kind of feedback loop at a time. Of course, in real systems feedback loops rarely come singly. They are linked together, often in fantastically complex patterns. A single stock is likely to have several reinforcing and balancing loops of differing strengths pulling it in several directions. A single flow may be adjusted by the contents of three or five or twenty stocks. It may fill one stock while it drains another and feeds into decisions that alter yet another. The many feedback loops in a system tug against each other, trying to make stocks grow, die off, or come into balance with each other. As a result, complex systems do much more than stay steady or explode exponentially or approach goals smoothly-as we shall see. 到目前为止，我的讨论仅限于一种反馈回路。当然，在实际系统中，反馈回路很少是单独存在的。它们联系在一起，往往形成极其复杂的模式。一只股票很可能有多个不同强度的强化和平衡回路，将其向多个方向拉动。一个流量可能会受到三个、五个或二十个存量的调整。它可能在填满一个存量的同时耗尽另一个存量，并为改变另一个存量的决策提供信息。系统中的许多反馈回路相互牵引，试图使存量增长、消亡或相互平衡。因此，复杂系统的作用远不止于保持稳定、呈指数增长或平稳接近目标--我们将会看到这一点。
A Brief Visit to the Systems Zoo 系统动物园简介
The ... goal of all theory is to make the . . . basic elements as simple and as few as possible without having to surrender the adequate representation of ... experience. 所有理论的......目标都是使......基本要素尽可能简单、尽可能少，而不必放弃对......经验的充分表述。
—Albert Einstein, physicist -阿尔伯特-爱因斯坦， 物理学家
One good way to learn something new is through specific examples rather than abstractions and generalities, so here are several common, simple but important examples of systems that are useful to understand in their own right and that will illustrate many general principles of complex systems. 学习新知识的一个好方法是通过具体的例子，而不是抽象和笼统的概念。因此，这里有几个常见、简单但重要的系统例子，它们本身就有助于理解，并能说明复杂系统的许多一般原理。
This collection has some of the same strengths and weaknesses as a zoo. It gives you an idea of the large variety of systems that exist in the world, but it is far from a complete representation of that variety. It groups the animals by family-monkeys here, bears there (single-stock systems here, two-stock systems there)—so you can observe the characteristic behaviors of monkeys, as opposed to bears. But, like a zoo, this collection is too neat. To make the animals visible and understandable, it separates them from each other and from their normal concealing environment. Just as zoo animals more naturally occur mixed together in ecosystems, so the systems animals described here normally connect and interact with each other and with others not illustrated hereall making up the buzzing, hooting, chirping, changing complexity in which we live. 这套书与动物园有一些相同的优缺点。 它让你了解到世界上存在着种类繁多的系统，但它远不能完全代表这些种类。它将动物按家族分组--这里是猴子，那里是熊（这里是单股系统，那里是双股系统）--因此你可以观察到猴子的特征行为，而不是熊的特征行为。但是，就像动物园一样，这套书过于整齐。为了让动物们看得见、摸得着，它把它们彼此分开，也把它们从正常的隐蔽环境中分离出来。就像动物园里的动物更自然地混杂在生态系统中一样，这里描述的系统动物通常也会相互联系、相互作用，并与其他未在此图示的动物一起构成我们生活的嗡嗡声、鸣叫声、啁啾声和不断变化的复杂环境。
Ecosystems come later. For the moment, let's look at one system animal at a time. 生态系统稍后再谈。现在，我们先来看看一个系统中的动物。
One-Stock Systems 单库存系统
A Stock with Two Competing Balancing Loops-a Thermostat 具有两个相互竞争的平衡回路的股票--恒温器
You already have seen the "homing in" behavior of the goal-seeking balancing feedback loop-the coffee cup cooling. What happens if there are two such loops, trying to drag a single stock toward two different goals? 您已经看到了寻求目标的平衡反馈回路的 "归位 "行为--咖啡杯冷却。如果有两个这样的回路，试图将一只股票拖向两个不同的目标，会发生什么情况呢？
One example of such a system is the thermostat mechanism that regulates the heating of your room (or cooling, if it is connected to an air conditioner instead of a furnace). Like all models, the representation of a thermostat in Figure 15 is a simplification of a real home heating system. 这种系统的一个例子就是调节房间供暖（或制冷，如果连接的是空调而不是火炉）的自动调温器。与所有模型一样，图 15 中的自动调温器也是对真实家庭供暖系统的简化。
Figure 15. Room temperature regulated by a thermostat and furnace. 图 15.室温由恒温器和炉子调节。
Whenever the room temperature falls below the thermostat setting, the thermostat detects a discrepancy and sends a signal that turns on the heat flow from the furnace, warming the room. When the room temperature rises again, the thermostat turns off the heat flow. This straightforward, stock-maintaining, balancing feedback loop is shown on the left side of Figure 15. If there were nothing else in the system, and if you start with a cold room with the thermostat set at , it would behave as shown in Figure 16. The furnace comes on, and the room warms up. When the room temperature reaches the thermostat setting, the furnace goes off, and the room stays right at the target temperature. 每当室温低于自动调温器的设定值时，自动调温器就会检测到差异并发出信号，从而开启火炉的热流，使室内升温。当室温再次升高时，自动调温器就会关闭热流。图 15 左侧显示了这一简单明了的库存维持平衡反馈回路。如果系统中没有任何其他设备，并且开始时房间很冷，恒温器的温度设定为 ，则系统的运行情况如图 16 所示。电炉开始工作，室内温度升高。当室温达到恒温器的设定值时，火炉熄灭，室内温度保持在目标温度。
However, this is not the only loop in the system. Heat also leaks to the outside. The outflow of heat is governed by the second balancing feedback loop, shown on the right side of Figure 15. It is always trying to make the room temperature equal to the outside, just like a coffee cup cooling. If 然而，这并不是系统中唯一的回路。热量也会向外泄漏。热量的流出由第二个平衡反馈回路控制，如图 15 右侧所示。它一直在努力使室温与室外温度相等，就像咖啡杯冷却一样。如果
Figure 16. A cold room warms quickly to the thermostat setting. 图 16.寒冷的房间会迅速升温至恒温器设定值。
Figure 17. A warm room cools very slowly to the outside temperature of . 图 17.温暖的房间缓慢冷却到室外温度 。
this were the only loop in the system (if there were no furnace), Figure 17 shows what would happen, starting with a warm room on a cold day. 如果系统中只有这个环路（如果没有炉子），图 17 显示了在寒冷的天气里从一个温暖的房间开始时会发生的情况。
The assumption is that room insulation is not perfect, and so some heat leaks out of the warm room to the cool outdoors. The better the insulation, the slower the drop in temperature would be. 假设房间的隔热性能并不完美，因此一些热量会从温暖的房间漏到凉爽的室外。隔热效果越好，温度下降的速度就越慢。
Now, what happens when these two loops operate at the same time? Assuming that there is sufficient insulation and a properly sized furnace, the heating loop dominates the cooling loop. You end up with a warm room (see Figure 18), even starting with a cold room on a cold day. 那么，当这两个回路同时运行时会发生什么情况呢？假设有足够的隔热材料和大小合适的炉子，那么供热环路将主导制冷环路。即使是在寒冷的天气里，从一个寒冷的房间开始，最终也会有一个温暖的房间（见图 18）。
Figure 18. The furnace warms a cool room, even as heat continues to leak from the room. 图 18.炉子为凉爽的房间供暖，但房间内的热量仍在继续泄漏。
As the room heats up, the heat flowing out of it increases, because there's a larger gap between inside and outside temperatures. But the furnace keeps putting in more heat than the amount that leaks out, so the room warms nearly to the target temperature. At that point, the furnace cycles off and on as it compensates for the heat constantly flowing out of the room. 随着房间升温，流出房间的热量也会增加，因为室内外温度之间的差距越来越大。但是，炉子不断输入的热量大于流出的热量，因此房间几乎升温到目标温度。此时，炉子会循环开关，以补偿不断流出房间的热量。
The thermostat is set at in this simulation, but the room temperature levels off slightly below . That's because of the leak to the outside, which is draining away some heat even as the furnace is getting the signal to put it back. This is a characteristic and sometimes surprising behavior of a system with competing balancing loops. It's like trying to keep a bucket full when there's a hole in the bottom. To make things worse, water leaking out of the hole is governed by a feedback loop; the more water in the bucket, the more the water pressure at the hole increases, so the flow out increases! In this case, we are trying to keep the room warmer than the outside and the warmer the room is, the faster it loses heat to the outside. It takes time for the furnace to correct for the increased heat loss-and in that minute still more heat leaks out. In a well-insulated house, the leak will be slower and so the house more comfortable than a poorly insulated one, even a poorly insulated house with a big furnace. 在此模拟中，恒温器的设定温度为 ，但室温略低于 。这是因为向室外泄漏了一些热量，甚至在炉子收到重新放热的信号时，热量也被排走了。这是有相互竞争的平衡回路的系统所特有的行为，有时会令人吃惊。这就好比桶底有个洞，却要把桶装满。更糟糕的是，从洞口漏出的水是受反馈回路控制的；桶里的水越多，洞口的水压就越大，因此流出的水也就越多！在这种情况下，我们试图让室内温度高于室外，而室内温度越高，向室外散失热量的速度就越快。炉子需要时间来修正增加的热量损失，而在这一分钟内，还会有更多的热量泄漏出去。在隔热性能良好的房屋中，热量泄漏的速度会更慢，因此房屋会比隔热性能差的房屋更舒适，即使是使用大火炉的隔热性能差的房屋也是如此。
With home heating systems, people have learned to set the thermostat slightly higher than the actual temperature they are aiming at. Exactly how much higher can be a tricky question, because the outflow rate is higher on cold days than on warm days. But for thermostats this control problem 对于家庭供暖系统，人们已经学会将恒温器设置得比实际温度稍高一些。究竟高出多少可能是个棘手的问题，因为冷天的出水率要高于暖天。但对于恒温器来说，这个控制问题
isn't serious. You can muddle your way to a thermostat setting you can live with. 并不严重。你可以用自己的方式找到一个可以接受的恒温器设置。
For other systems with this same structure of competing balancing loops, the fact that the stock goes on changing while you're trying to control it can create real problems. For example, suppose you're trying to maintain a store inventory at a certain level. You can't instantly order new stock to make up an immediately apparent shortfall. If you don't account for the goods that will be sold while you are waiting for the order to come in, your inventory will never be quite high enough. You can be fooled in the same way if you're trying to maintain a cash balance at a certain level, or the level of water in a reservoir, or the concentration of a chemical in a continuously flowing reaction system. 对于其他具有相同竞争平衡循环结构的系统来说，当你试图控制库存时，库存却在不断变化，这可能会带来真正的问题。例如，假设你想把商店的库存维持在一定水平。你不能立即订购新的存货来弥补明显的短缺。如果你不考虑在等待订单的过程中会售出的货物，你的库存就永远不会足够高。如果你想把现金余额保持在某个水平，或把水库中的水位保持在某个水平，或把持续流动的反应系统中的化学物质浓度保持在某个水平，你也会被同样的方式愚弄。
There's an important general principle here, and also one specific to the thermostat structure. First the general one: The information delivered by a feedback loop can only affect future behavior; it can't deliver the information, and so can't have an impact fast enough to correct behavior that drove the current feedback. A person in the system who makes a decision based on the feedback can't change the behavior of the system that drove the current feedback; the decisions he or she makes 这里有一个重要的一般原则，也有一个恒温器结构特有的原则。首先是一般原则：反馈回路所传递的信息只能影响未来的行为；它无法传递信息，因此也就无法产生足够快的影响来纠正驱动当前反馈的行为。系统中根据反馈做出决定的人，无法改变驱动当前反馈的系统行为；他或她做出的决定
will affect only future behavior. 只会影响未来的行为。
Why is that important? Because it means there will always be delays in responding. It says that a flow can't react instantly to a flow. It can react only to a change in a stock, and only after a slight delay to register the incoming information. In the bathtub, it takes a split second of time to assess the depth of the water and decide to adjust the flows. Many economic models make a mistake in this matter by assuming that consumption or produc- 为什么这很重要？因为这意味着响应总是会有延迟。这就是说，流量不可能立即对流量做出反应。它只能对存量的变化做出反应，而且只能在稍作延迟后才能对接收到的信息做出反应。在浴缸中，需要一瞬间的时间来评估水的深度并决定调整流量。许多经济模型在这个问题上都犯了一个错误，即假定消费或生产都是在一瞬间发生的。
The information delivered by a feedback loop-even nonphysical feedbackcan only affect future behavior; it can't deliver a signal fast enough to correct behavior that drove the current feedback. Even nonphysical information takes time to feedback into the system. tion can respond immediately, say, to a change in price. That's one of the reasons why real economies tend not to behave exactly like many economic models. 反馈回路传递的信息，即使是非物理反馈，也只能影响未来的行为；它无法快速传递信号，纠正驱动当前反馈的行为。即使是非物理信息也需要时间才能反馈到系统中。这就是为什么现实经济的行为往往与许多经济模型不完全相同的原因之一。
The specific principle you can deduce from this simple system is that you must remember in thermostat-like systems to take into account whatever draining or filling processes are going on. If you don't, you won't achieve the target level of your stock. If you want your room temperature to be at , you have to set the thermostat a little above the desired 从这个简单的系统中可以得出的具体原则是，在类似恒温器的系统中，您必须记住要考虑到正在进行的任何排水或填充过程。否则，就无法达到目标库存水平。如果您希望室温保持在 ，则必须将恒温器设置得比所需温度稍高一些。
temperature. If you want to pay off your credit card (or the national debt), you have to raise your repayment rate high enough to cover the charges you incur while you're paying (including interest). If you're gearing up your work force to a higher level, you have to hire fast enough to correct for 温度。如果你想还清你的信用卡（或国债），你必须把还款率提高到足以支付你在还款时产生的费用（包括利息）。如果您想让您的员工队伍更上一层楼，您就必须加快招聘速度，以弥补以下不足
A stock-maintaining balancing feedback loop must have its goal set appropriately to compensate for draining or inflowing processes that affect that stock. Otherwise, the feedback process will fall short of or exceed the target for the stock. those who quit while you are hiring. In other words, your mental model of the system needs to include all the important flows, or you will be surprised by the system's behavior. 维持存量的平衡反馈回路必须适当设定目标，以补偿影响存量的流失或流入过程。否则，反馈过程就会低于或超过存量的目标。换句话说，你的系统心智模型必须包含所有重要的流程，否则你就会对系统的行为感到惊讶。
Before we leave the thermostat, we should see how it behaves with a varying outside temperature. Figure 19 shows a twenty-four-hour period of normal operation of a well-functioning thermostat system, with the outside temperature dipping well below freezing. The inflow of heat from the furnace nicely tracks the outflow of heat to the outside. The temperature in the room varies hardly at all once the room has warmed up. 在离开恒温器之前，我们应该看看恒温器在室外温度变化时的表现。图 19 显示了一个功能良好的恒温器系统正常运行 24 小时的情况，室外温度降到了零度以下。炉子的热量流入很好地跟踪了热量流出室外的情况。一旦房间暖和起来，室内温度几乎没有变化。
Every balancing feedback loop has its breakdown point, where other loops pull the stock away from its goal more strongly than it can pull back. That can happen in this simulated thermostat system, if I weaken the power of the heating loop (a smaller furnace that cannot put out as much heat), or if I strengthen the power of the cooling loop (colder outside tempera- 每个平衡反馈回路都有其崩溃点，在这个崩溃点上，其他回路会将存量从其目标上拉开，而不是将其拉回来。在这个模拟恒温器系统中，如果我削弱了加热环路的功率（炉子变小，不能释放出那么多热量），或者我加强了冷却环路的功率（室外温度变低），就会出现这种情况。
Figure 19. The furnace warms a cool room, even as heat leaks from the room and outside temperatures drop below freezing. 图 19.即使房间漏出热量，室外温度降至零度以下，火炉也能为凉爽的房间供暖。
ture, less insulation, or larger leaks). Figure 20 shows what happens with the same outside temperatures as in Figure 19, but with faster heat loss from the room. At very cold temperatures, the furnace just can't keep up with the heat drain. The loop that is trying to bring the room temperature down to the outside temperature dominates the system for a while. The room gets pretty uncomfortable! 图 20 显示了在室外温度与图 19 相同，但室内热量损失较快的情况。）图 20 显示了在室外温度与图 19 相同的情况下，室内热量损失更快的情况。在非常寒冷的温度下，炉子无法跟上热量流失的速度。试图将室温降至室外温度的环路会在一段时间内主导系统。房间会变得非常不舒服！
Figure 20. On a cold day, the furnace can't keep the room warm in this leaky house! 图 20.在寒冷的日子里，这个漏水的房子里的炉子无法保持室内温暖！
See if you can follow, as time unfolds, how the variables in Figure 20 relate to one another. At first, both the room and the outside temperatures are cool. The inflow of heat from the furnace exceeds the leak to the outside, and the room warms up. For an hour or two, the outside is mild enough that the furnace replaces most of the heat that's lost to the outside, and the room temperature stays near the desired temperature. 看看您能否随着时间的推移，了解图 20 中各变量之间的关系。起初，室内和室外的温度都很低。从炉子中流入的热量超过了向室外泄漏的热量，室内温度升高。在一两个小时内，室外温度较低，炉子可以补充大部分向室外散失的热量，室温保持在理想温度附近。
But as the outside temperature falls and the heat leak increases, the furnace cannot replace the heat fast enough. Because the furnace is generating less heat than is leaking out, the room temperature falls. Finally, the outside temperature rises again, the heat leak slows, and the furnace, still operating at full tilt, finally can pull ahead and start to warm the room again. 但是，随着室外温度的降低和热量泄漏的增加，火炉无法快速补充热量。由于炉子产生的热量少于漏出的热量，室温随之下降。最后，室外温度再次升高，热量泄漏速度减慢，仍在全速运行的火炉终于可以提前开始为房间供暖。
Just as in the rules for the bathtub, whenever the furnace is putting in more heat than is leaking out, the room temperature rises. Whenever the inflow rate falls behind the outflow rate, the temperature falls. If you 就像浴缸的规则一样，每当炉子输入的热量多于漏出的热量时，室温就会升高。只要流入的热量少于流出的热量，温度就会下降。如果您
study the system changes on this graph for a while and relate them to the feedback-loop diagram of this system, you'll get a good sense of how the structural interconnections of this system-its two feedback loops and how they shift in strength relative to each other-lead to the unfolding of the system's behavior over time. 如果你能对这张图上的系统变化进行一段时间的研究，并将它们与这个系统的反馈回路图联系起来，你就会很好地理解这个系统的结构性相互联系--它的两个反馈回路以及它们的强度如何相对变化--是如何随着时间的推移而导致系统行为的展开的。
A Stock with One Reinforcing Loop and One Balancing Loop-Population and 具有一个强化环路和一个平衡环路的股票--人口与
Industrial Economy 工业经济
What happens when a reinforcing and a balancing loop are both pulling on the same stock? This is one of the most common and important system structures. Among other things, it describes every living population and every economy. 当加强环和平衡环同时拉动同一股票时，会发生什么情况？这是最常见、最重要的系统结构之一。除其他外，它还描述了每一个有生命的群体和每一个经济体。
Figure 21. Population governed by a reinforcing loop of births and a balancing loop of deaths. 图 21.人口受出生强化循环和死亡平衡循环的制约。
A population has a reinforcing loop causing it to grow through its birth rate, and a balancing loop causing it to die off through its death rate. 一个种群有一个强化循环，通过出生率使种群增长，也有一个平衡循环，通过死亡率使种群消亡。
As long as fertility and mortality are constant (which in real systems they rarely are), this system has a simple behavior. It grows exponentially or dies off, depending on whether its reinforcing feedback loop determining births is stronger than its balancing feedback loop determining deaths. 只要生育率和死亡率保持不变（在现实系统中很少如此），这个系统的行为就很简单。它是呈指数增长还是消亡，取决于决定出生的强化反馈回路是否强于决定死亡的平衡反馈回路。
For example, the 2007 world population of 6.6 billion people had a fertility rate of roughly 21 births a year for every 1,000 people in the population. Its mortality rate was 9 deaths a year out of every 1,000 people. Fertility was higher than mortality, so the reinforcing loop dominated the system. If those fertility and mortality rates continue unchanged, a child born 例如，2007 年世界人口为 66 亿，生育率约为每 1 000 人每年出生 21 人。死亡率为每 1000 人中每年有 9 人死亡。生育率高于死亡率，因此强化循环在整个系统中占主导地位。如果生育率和死亡率继续保持不变，那么出生的孩子
Figure 22. Population growth if fertility and mortality maintain their 2007 levels of 21 births and nine deaths per 1,000 people. 图 22.如果生育率和死亡率保持 2007 年每千人 21 例出生和 9 例死亡的水平，人口增长情况。
now will see the world population more than double by the time he or she reaches the age of 60, as shown in Figure 22. 如图 22 所示，到 60 岁时，世界人口将增加一倍多。
If, because of a terrible disease, the mortality rate were higher, say at 30 deaths per 1,000 , while the fertility rate remained at 21 , then the death loop 如果由于某种可怕的疾病，死亡率升高，例如每 1 000 人中有 30 人死亡，而生育率仍为 21，那么死亡圈
Figure 23. Population decline if fertility remains at 2007 level (21 births per 1,000) but mortality is much higher, 30 deaths per 1,000 . 图 23.如果生育率保持在 2007 年的水平（每 1 000 人出生 21 人），但死亡率大幅上升（每 1 000 人死亡 30 人），则人口下降。
would dominate the system. More people would die each year than would be born, and the population would gradually decrease (Figure 23). 将主导整个系统。每年死亡的人将多于出生的人，人口将逐渐减少（图 23）。
Things get more interesting when fertility and mortality change over time. When the United Nations makes long-range population projections, it generally assumes that, as countries become more developed, average fertility will decline (approaching replacement where on average each woman has 1.85 children). Until recently, assumptions about mortality were that it would also decline, but more slowly (because it is already low in most parts of the world). However, because of the epidemic of HIV/ AIDS, the UN now assumes the trend of increasing life expectancy over the next fifty years will slow in regions affected by HIV/AIDS. 当生育率和死亡率随时间发生变化时，情况就变得更加有趣了。联合国在进行长期人口预测时，通常假定随着国家变得越来越发达，平均生育率将下降（接近更替期，即平均每个妇女生育 1.85 个孩子）。直到最近，关于死亡率的假设是，死亡率也会下降，但下降速度较慢（因为世界上大多数地区的死亡率已经很低）。然而，由于艾滋病毒/艾滋病的流行，联合国现在假定，在受艾滋病毒/艾滋病影响的地区，未来五十年预期寿命延长的趋势将放缓。
Changing flows (fertility and mortality) create a change in the behavior over time of the stock (population)—the line bends. If, for example, world fertility falls steadily to equal mortality by the year 2035 and they both stay 流量（生育率和死亡率）的变化会导致存量（人口）的行为随时间发生变化--即线弯曲。例如，如果世界生育率持续下降，到 2035 年与死亡率持平，并且两者都保持
Figure 24. Population stabilizes when fertility equals mortality. 图 24当生育率等于死亡率时，人口趋于稳定。
constant thereafter, the population will level off, births exactly balancing deaths in dynamic equilibrium, as in Figure 24. 此后，人口将趋于稳定，出生人数与死亡人数完全平衡，达到动态平衡，如图 24 所示。
This behavior is an example of shifting dominance of feedback loops. Dominance is an important concept in systems thinking. When one loop dominates another, it has a stronger impact on behavior. Because systems often have several competing feedback loops operating simultaneously, those loops that dominate the system will determine the behavior. 这种行为就是反馈回路主导权转移的一个例子。主导性是系统思维中的一个重要概念。当一个环路主导另一个环路时，它对行为的影响就更大。由于系统通常有多个相互竞争的反馈回路同时运行，因此主导系统的回路将决定系统的行为。
At first, when fertility is higher than mortality, the reinforcing growth loop dominates the system and the resulting behavior is exponential 起初，当生育率高于死亡率时，强化增长循环会主导系统，由此产生的行为是指数型的
growth. But that loop is gradually weakened as fertility falls. Finally, it exactly equals the strength of the balancing loop of mortality. At that point neither loop dominates, and we have dynamic equilibrium. 增长。但随着生育率的下降，这一循环逐渐减弱。最后，它与死亡率的平衡环的强度完全相等。此时，两个环路都不占主导地位，我们就达到了动态平衡。
You saw shifting dominance in the thermostat system, when the outside temperature fell and the heat leaking out of the poorly insulated house overwhelmed the ability of the furnace to put heat into the room. Dominance shifted from the heating loop to the cooling loop. 当室外温度下降，隔热性能差的房屋漏出的热量压倒了火炉向室内供热的能力时，你就会看到恒温器系统的主导权发生了变化。主导权从供热环路转移到了制冷环路。
Complex behaviors of systems often arise as the relative strengths of feedback loops shift, causing first one loop and then another to dominate behavior. 系统的复杂行为往往是由于反馈回路的相对强度发生了变化，先是一个回路，然后是另一个回路主导了行为。
There are only a few ways a population system could behave, and these depend on what happens to the "driving" variables, fertility and mortality. These are the only ones possible for a simple system of one reinforcing and one balancing loop. A stock governed by linked reinforcing and balancing loops will grow exponentially if the reinforcing loop dominates the balancing one. It will die off if the balancing loop dominates the reinforcing one. It will level off if the two loops are of equal strength (see Figure 25). Or it will do a sequence of these things, one after another, if the relative strength of the two loops change over time (see Figure 26). 人口系统只有几种表现形式，它们取决于 "驱动 "变量--生育率和死亡率--的变化情况。对于只有一个强化循环和一个平衡循环的简单系统来说，只有这几种可能。如果强化环路支配平衡环路，则受强化环路和平衡环路联动支配的种群将呈指数增长。如果平衡环路在强化环路中占主导地位，股票就会消亡。如果两个循环的强度相当，则会趋于平稳（见图 25）。或者，如果两个环路的相对强度随着时间的推移发生变化，则会出现上述一系列情况（见图 26）。
I chose some provocative population scenarios here to illustrate a point about models and the scenarios they can generate. Whenever you are confronted with a scenario (and you are, every time you hear about an economic prediction, a corporate budget, a weather forecast, future climate change, a stockbroker saying what is going to happen to a particular holding), there are questions you need to ask that will help you decide how good a representation of reality is the underlying model. 我在这里选择了一些挑衅性的人口情景，以说明关于模型及其所能产生的情景的一个观点。每当你面对一个假设情景时（每次你听到经济预测、公司预算、天气预报、未来气候变化、股票经纪人说某只股票会发生什么变化时，你都会遇到这样的情景），你需要问一些问题，这些问题将帮助你判断基础模型对现实的反映有多好。
Are the driving factors likely to unfold this way? (What are birth rate and death rate likely to do?) 驱动因素是否可能如此发展？(出生率和死亡率可能会怎样？）
If they did, would the system react this way? (Do birth and death rates really cause the population stock to behave as we think it will?) 如果是这样，系统会做出这样的反应吗？(出生率和死亡率真的会导致人口存量像我们想象的那样变化吗？）
-What is driving the driving factors? (What affects birth rate? What affects death rate?) -驱动因素是什么？(是什么影响了出生率？ 是什么影响了死亡率？）
The first question can't be answered factually. It's a guess about the future, and the future is inherently uncertain. Although you may have a strong 第一个问题无法用事实来回答。这是对未来的猜测，而未来本来就是不确定的。虽然你可能有强烈的
A: Growth 答：增长
B: Decline B: 下降
C: Stabilization C：稳定
Figure 25. Three possible behaviors of a population: growth, decline, and stabilization. 图 25.人口的三种可能行为：增长、下降和稳定。
opinion about it, there's no way to prove you're right until the future actually happens. A systems analysis can test a number of scenarios to see what happens if the driving factors do different things. That's usually one purpose of a systems analysis. But you have to be the judge of which scenario, if any, should be taken seriously as a future that might really be possible. 在未来真正发生之前，我们无法证明自己是正确的。系统分析可以测试多种情况，看看如果驱动因素做不同的事情会发生什么。这通常是系统分析的目的之一。但是，你必须判断哪种情况（如果有的话）应该被认真对待，将其视为真正可能发生的未来。
Figure 26. Shifting dominance of fertility and mortality loops. 图 26.生育率和死亡率循环的主导地位变化。
Dynamic systems studies usually are not designed to predict what will happen. Rather, they're designed to explore what would happen, if a number of driving factors unfold in a range of different ways. 动态系统研究通常不是为了预测会发生什么。相反，它们旨在探索如果一些驱动因素以一系列不同的方式展开，将会发生什么。
The second question-whether the system really will react this way-is more scientific. It's a question about how good the model is. Does it capture the inherent dynamics of the system? Regardless of whether you think the driving factors will do that, would the system behave like that if they did? 第二个问题--系统是否真的会做出这样的反应--更为科学。这是一个关于模型好坏的问题。它能捕捉到系统的内在动态吗？不管你认为驱动因素是否会这样做，如果它们真的这样做了，系统会有这样的表现吗？
In the population scenarios above, however System dynamics models likely you think they are, the answer to this explore possible futures and ask "what if" questions. second question is roughly yes, the population would behave like this, if the fertility and mortality did that. The population model I have used here is very simple. A more detailed model would distinguish age groups, for example. But basically this model responds the way a real population would, growing under the conditions when a real 在上述人口情景中，无论你认为系统动力学模型有多大的可能性，答案都是探索可能的未来，并提出 "如果 "的问题。第二个问题大致是肯定的，如果生育率和死亡率是这样，人口就会这样。我在这里使用的人口模型非常简单。更详细的模型会区分年龄组等。但基本上，这个模型的反应方式与真实人口的反应方式相同，即在真实人口增长的条件下增长。
QUESTIONS FOR TESTING THE VALUE OF A MODEL 检验模型价值的问题
Are the driving factors likely to unfold this way? 驱动因素有可能这样发展吗？
If they did, would the system react this way? 如果是这样，系统会有这样的反应吗？
What is driving the driving factors? 驱动因素是什么？
Model utility depends not on whether its driving scenarios are realistic (since no one can know that for sure), but on whether it responds with a realistic pattern of behavior. 模型的效用并不取决于它的驾驶场景是否真实（因为没有人能确定这一点），而是取决于它是否以真实的行为模式做出反应。
population would grow, declining when a real population would decline. The numbers are off, but the basic behavior pattern is realistic. 人口会增长，而实际人口会减少。数字有偏差，但基本行为模式是真实的。
Finally, there is the third question. What is driving the driving factors? What is adjusting the inflows and outflows? This is a question about system boundaries. It requires a hard look at those driving factors to see if they are actually independent, or if they are also embedded in the 最后是第三个问题。什么是驱动因素？是什么在调整流入和流出？这是一个关于系统边界的问题。这就要求我们认真研究这些驱动因素，看看它们实际上是独立的，还是也蕴含在系统中。
system. 系统
Is there anything about the size of the population, for instance, that might feed back to influence fertility or mortality? Do other factors-economics, the environment, social trends-influence fertility and mortality? Does the size of the population affect those economic and environmental and social factors? 例如，人口数量是否会影响生育率或死亡率？其他因素--经济、环境、社会趋势--是否影响生育率和死亡率？人口数量是否会影响这些经济、环境和社会因素？
Of course, the answer to all of these questions is yes. Fertility and mortality are governed by feedback loops too. At least some of those feedback loops are themselves affected by the size of the population. This population "animal" is only one piece of a much larger system. 当然，所有这些问题的答案都是肯定的。生育率和死亡率也受反馈回路的制约。至少其中一些反馈回路本身会受到人口规模的影响。人口 "动物 "只是一个更大系统中的一个部分。
One important piece of the larger system that affects population is the economy. At the heart of the economy is another reinforcing-loop-plusbalancing-loop system-the same kind of structure, with the same kinds 经济是影响人口的大系统中的一个重要部分。经济的核心是另一个强化循环加平衡循环系统。
Figure 27. Like a living population, economic capital has a reinforcing loop (investment of output) governing growth and a balancing loop (depreciation) governing decline. 图 27.与有生命的人口一样，经济资本也有一个促进增长的循环（产出投资）和一个平衡衰退的循环（折旧）。
of behavior, as the population (see Figure 27). 的行为（见图 27）。
The greater the stock of physical capital (machines and factories) in the economy and the efficiency of production (output per unit of capital), the more output (goods and services) can be produced each year. 经济中的物质资本（机器和工厂）存量越大，生产效率（单位资本产出）越高，每年就能生产出更多的产出（商品和服务）。
The more output that is produced, the more can be invested to make new capital. This is a reinforcing loop, like the birth loop for a population. The investment fraction is equivalent to the fertility. The greater the fraction of its output a society invests, the faster its capital stock will grow. 产出越多，就有越多的资金投入到新的资本中。这是一个强化循环，就像人口的出生循环一样。投资比例相当于生育率。社会产出的投资部分越大，其资本存量的增长速度就越快。
Physical capital is drained by depreciation-obsolescence and wearingout. The balancing loop controlling depreciation is equivalent to the death loop in a population. The "mortality" of capital is determined by the average capital lifetime. The longer the lifetime, the smaller the fraction of capital that must be retired and replaced each year. 有形资本因折旧--陈旧和磨损而耗尽。控制折旧的平衡循环相当于人口的死亡循环。资本的 "死亡率 "由资本的平均寿命决定。寿命越长，每年必须报废和更换的资本比例就越小。
If this system has the same structure as the population system, it must have the same repertoire of behaviors. Over recent history world capital, like world population, has been dominated by its reinforcing loop and has been growing exponentially. Whether in the future it grows or stays constant or dies off depends on whether its reinforcing growth loop remains stronger than its balancing depreciation loop. That depends on 如果这个系统与人口系统具有相同的结构，那么它也必然具有相同的行为方式。在近代史上，世界资本与世界人口一样，一直被其强化循环所支配，并呈指数级增长。未来，世界资本是增长、保持不变还是消亡，取决于其强化增长循环是否仍然强于其平衡折旧循环。这取决于
the investment fraction-how much output the society invests rather than consumes, 投资部分--社会投资而非消费了多少产出、
the efficiency of capital—how much capital it takes to produce a given amount of output, and 资本效率--生产一定量的产出需要多少资本，以及
the average capital lifetime. 平均资本寿命。
If a constant fraction of output is reinvested in the capital stock and the efficiency of that capital (its ability to produce output) is also constant, the capital stock may decline, stay constant, or grow, depending on the lifetime of the capital. The lines in Figure 28 show systems with different average capital lifetimes. With a relatively short lifetime, the capital wears out faster than it is replaced. Reinvestment does not keep up with depreciation and the economy slowly declines. When depreciation just balances investment, the economy is in dynamic equilibrium. With a long lifetime, the capital stock grows exponentially. The longer the lifetime of capital, the faster it grows. 如果产出的固定部分再投资于资本存量，并且资本的效率（生产产出的能力）也保持不变，那么资本存量可能会下降、保持不变或增长，这取决于资本的寿命。图 28 中的线条显示了不同平均资本寿命的系统。资本寿命相对较短时，资本的损耗速度快于资本的更新速度。再投资跟不上折旧，经济缓慢衰退。当折旧刚好与投资平衡时，经济处于动态平衡。如果资本寿命长，资本存量就会呈指数增长。资本寿命越长，增长速度越快。
This is another example of a principle we've already encountered: You can make a stock grow by decreasing its outflow rate as well as by increas- 这是我们已经遇到过的原理的另一个例子：你可以通过降低股票的流出率来使其增长，也可以通过提高股票的流出率来使其增长。
Figure 28. Growth in capital stock with changes in the lifetime of the capital. In a system with output per unit capital ratio of 1:3 and an investment fraction of 20 percent, capital with a lifetime of 15 years just keeps up with depreciation. A shorter lifetime leads to a declining stock of capital. 图 28.资本存量的增长与资本寿命的变化。在单位资本产出比为 1:3、投资比例为 20%的系统中，使用寿命为 15 年的资本刚刚跟上折旧。寿命越短，资本存量越少。
ing its inflow rate! 流入率！
Just as many factors influence the fertility and mortality of a population, so many factors influence the output ratio, investment fraction, and the lifetime of capital—interest rates, technology, tax policy, consumption habits, and prices, to name just a few. Population itself influences investment, both by contributing labor to output, and by increasing demands on consumption, thereby decreasing the investment fraction. Economic output also feeds back to influence population in many ways. A richer economy usually has better health care and a lower death rate. A richer economy also usually has a lower birth rate. 影响人口生育率和死亡率的因素很多，影响产出率、投资比例和资本寿命的因素也很多，如利率、技术、税收政策、消费习惯和价格等等。人口本身对投资也有影响，它既可以为产出贡献劳动力，也可以增加对消费的需求，从而降低投资比例。经济产出也以多种方式反作用于人口。较富裕的经济体通常拥有较好的医疗保健和较低的死亡率。较富裕的经济体通常出生率也较低。
In fact, just about any long-term model of a real economy should link together the two structures of population and capital to show how they affect each other. The central question of economic development is how to keep the reinforcing loop of capital accumulation from growing more slowly than the reinforcing loop of population growth-so that people are 事实上，任何一个长期的实体经济模型都应该把人口和资本这两种结构联系起来，说明它们是如何相互影响的。经济发展的核心问题是，如何使资本积累的强化循环的增长速度不超过人口增长的强化循环的增长速度，从而使人
Systems with similar feedback structures produce similar dynamic behaviors. getting richer instead of poorer. 具有相似反馈结构的系统会产生相似的动态行为。
It may seem strange to you that I call the capital system the same kind of "zoo animal" as the population system. A production system with factories and shipments and economic flows doesn't look much like a population system with babies being born and people aging 我把资本系统称为与人口系统同类的 "动物园动物"，你可能会觉得奇怪。有工厂、运输和经济流动的生产系统与有婴儿出生和人口老龄化的人口系统看起来并不太一样。
and having more babies and dying. But from a systems point of view these systems, so dissimilar in many ways, have one important thing in common: their feedback-loop structures. Both have a stock governed by a reinforcing growth loop and a balancing death loop. Both also have an aging process. Steel mills and lathes and turbines get older and die just as people do. 生更多的孩子和死亡。但是，从系统的角度来看，这些在许多方面如此不同的系统有一个重要的共同点：它们的反馈回路结构。两者都有一个由强化增长环和平衡死亡环支配的存量。两者都有一个老化过程。钢厂、车床和涡轮机都会老化和死亡，就像人一样。
One of the central insights of systems theory, as central as the observation that systems largely cause their own behavior, is that systems with similar feedback structures produce similar dynamic behaviors, even if the outward appearance of these systems is completely dissimilar. 系统理论的核心观点之一，与系统在很大程度上导致自身行为的观点一样，是具有相似反馈结构的系统会产生相似的动态行为，即使这些系统的外表完全不同。
A population is nothing like an industrial economy, except that both can reproduce themselves out of themselves and thus grow exponentially. And both age and die. A coffee cup cooling is like a warmed room cooling, and like a radioactive substance decaying, and like a population or industrial economy aging and dying. Each declines as the result of a balancing feedback loop. 人口与工业经济完全不同，只是两者都能自我繁殖，从而呈指数增长。两者都会衰老和死亡。咖啡杯冷却就像温暖的房间冷却，就像放射性物质衰变，就像人口或工业经济老化和死亡。每一种衰退都是平衡反馈循环的结果。
A System with Delays-Business Inventory 有延迟的系统--商业库存
Picture a stock of inventory in a store-a car dealership—with an inflow of deliveries from factories and an outflow of new car sales. By itself, this stock of cars on the dealership lot would behave like the water in a bathtub. 想象一下一家商店--汽车经销店--的库存情况：工厂发货，新车销售。就其本身而言，汽车经销商处的汽车库存就像浴缸里的水一样。
Figure 29. Inventory at a car dealership is kept steady by two competing balancing loops, one through sales and one through deliveries. 图 29.汽车经销商的库存是通过两个相互竞争的平衡循环来保持稳定的，一个是销售，另一个是交付。
Now picture a regulatory feedback system designed to keep the inventory high enough so that it can always cover ten days' worth of sales (see Figure 29). The car dealer needs to keep some inventory because deliveries and purchases don't match perfectly every day. Customers make purchases that are unpredictable on a day-to-day basis. The car dealer also needs to provide herself with some extra inventory (a buffer) in case deliveries from suppliers are delayed occasionally. 现在设想一个监管反馈系统，其目的是保持足够高的库存，使其总能满足十天的销售量（见图 29）。汽车经销商需要保持一定的库存，因为每天的交货量和购买量并不完全匹配。客户每天的购买量是不可预测的。汽车经销商还需要为自己准备一些额外的库存（缓冲），以防供应商偶尔延迟交货。
The dealer monitors sales (perceived sales), and if, for example, they seem to be rising, she adjusts orders to the factory to bring inventory up to her new desired inventory that provides ten days' coverage at the higher sales rate. So, higher sales mean higher perceived sales, which means a higher discrepancy between inventory and desired inventory, which means higher orders, which will bring in more deliveries, which will raise inventory so it can comfortably supply the higher rate of sales. 经销商监控销售额（感知销售额），例如，如果销售额似乎在上升，她就会调整给工厂的订单，使库存达到她新的期望库存，以便在较高的销售率下提供十天的供应。因此，较高的销售额意味着较高的感知销售额，这意味着库存与期望库存之间的差异增大，这意味着较高的订单量，这将带来更多的交货量，从而提高库存量，使其能够舒适地供应较高的销售率。
This system is a version of the thermostat system-one balancing loop of sales draining the inventory stock and a competing balancing loop maintaining the inventory by resupplying what is lost in sales. Figure 30 shows the not very surprising result of an increase in consumer demand of 10 percent. 该系统是恒温器系统的一个版本--销售平衡循环消耗库存存货，竞争平衡循环通过补充销售损失的存货来维持库存。图 30 显示了消费者需求增加 10% 后并不令人惊讶的结果。
In Figure 31, I am putting something else into this simple model—three delays that are typical of what we experience in the real world. 在图 31 中，我在这个简单的模型中加入了其他东西--我们在现实世界中经历的典型的三种延迟。
First, there is a perception delay, intentional in this case. The car dealer doesn't react to just any blip in sales. Before she makes ordering decisions, 首先，存在感知延迟，在这种情况下是故意的。汽车经销商不会对销售中的任何小插曲做出反应。在她做出订购决定之前
Figure 30. Inventory on the car dealership's lot with a permanent 10 -percent increase in consumer demand starting on day 25 . 图 30.在消费者需求从第 25 天开始持续增长 10%的情况下，汽车经销商的库存情况。
Figure 31. Inventory at a car dealership with three common delays now included in the picture-a perception delay, a response delay, and a delivery delay. 图 31.汽车经销商的库存，图片中包括三种常见延迟--感知延迟、响应延迟和交付延迟。
she averages sales over the past five days to sort out real trends from temporary dips and spikes. 她将过去五天的销售额平均化，以便从暂时的下跌和飙升中分辨出真正的趋势。
Second, there is a response delay. Even when it's clear that orders need to be adjusted, she doesn't try to make up the whole adjustment in a single order. Rather, she makes up one-third of any shortfall with each order. Another way of saying that is, she makes partial adjustments over three days to be extra sure the trend is real. Third, there is a delivery delay. It takes five days for the supplier at the factory to receive an order, process it, and 第二，反应迟缓。即使很明显需要调整订单，她也不会试图在一次订单中弥补全部调整额。相反，她会在每张订单中弥补三分之一的不足。另一种说法是，她在三天内进行部分调整，以确保趋势是真实的。第三，交货延迟。工厂的供应商需要五天时间来接收订单、处理订单并
Figure 32. Response of inventory to a 10 -percent increase in sales when there are delays in the system. 图 32.当系统出现延迟时，库存对销售额增长 10%的反应。
deliver it to the dealership. 把它送到车行。
Although this system still consists of just two balancing loops, like the simplified thermostat system, it doesn't behave like the thermostat system. Look at what happens, for example, as shown in Figure 32, when the business experiences the same permanent 10 -percent jump in sales from an increase in customer demand. 虽然这个系统仍然像简化的恒温器系统一样，只由两个平衡回路组成，但它的行为却与恒温器系统不同。例如，如图 32 所示，当企业的销售额因客户需求增加而永久性地增长 10%时，会发生什么情况？
Oscillations! A single step up in sales causes inventory to drop. The car dealer watches long enough to be sure the higher sales rate is going to last. Then she begins to order more cars to both cover the new rate of sales and bring the inventory up. But it takes time for the orders to come in. During that time inventory drops further, so orders have to go up a little more, to bring inventory back up to ten days' coverage. 震荡！销售量的上升会导致库存下降。汽车经销商观察足够长的时间，以确定较高的销售率会持续下去。然后，她开始订购更多的汽车，以满足新的销售率并增加库存。但订单的到来需要时间。在此期间，库存进一步下降，因此订单量必须再增加一些，才能使库存恢复到十天的水平。
Eventually, the larger volume of orders starts arriving, and inventory recovers-and more than recovers, because during the time of uncertainty about the actual trend, the owner has ordered too much. She now sees her mistake, and cuts back, but there are still high past orders coming in, so she orders even less. In fact, almost inevitably, since she still can't be sure of what is going to happen next, she orders too little. Inventory gets too low again. And so forth, through a series of oscillations around the new desired inventory level. As Figure 33 illustrates, what a difference a few delays make! 最终，大量订单开始到达，库存恢复了，而且恢复得还不止，因为在不确定实际趋势的那段时间里，店主订购了太多的订单。她现在认识到了自己的错误，于是减少了订货量，但过去的订单量仍然很大，所以她的订货量就更少了。事实上，几乎不可避免的是，由于她仍然无法确定下一步会发生什么，她的订单就会太少。库存再次变得过低。如此往复，围绕新的理想库存水平进行一系列震荡。如图 33 所示，几次延迟带来的影响是多么巨大！
We'll see in a moment that there are ways to damp these oscillations in inventory, but first it's important to understand why they occur. It isn't because the car dealer is stupid. It's because she is struggling to operate 我们马上就会看到抑制库存振荡的方法，但首先必须了解它们发生的原因。这并不是因为汽车经销商愚蠢。而是因为她在努力经营
A delay in a balancing feedback loop makes a system likely to oscillate. in a system in which she doesn't have, and can't have, timely information and in which physical delays prevent her actions from having an immediate effect on inventory. She doesn't know what her customers will do next. When they do something, she's not sure they'll keep doing it. When she issues an order, she doesn't see an immediate response. This situation of information insufficiency and physical delays is very common. Oscillations like these are frequently encountered in inventories and in many other systems. Try taking a shower sometime where there's a very long pipe between the hot- and cold-water mixer and the showerhead, and you'll experience directly the joys of hot and cold oscillations because of a long response delay. 在一个系统中，她没有也不可能及时获得信息，而物理延迟又使她的行动无法对库存产生立竿见影的效果。她不知道客户下一步会做什么。当他们做某事时，她不确定他们是否会继续这样做。当她发出订单时，她看不到立即的回应。这种信息不足和实际延误的情况非常普遍。在库存和许多其他系统中，经常会遇到类似的波动。试着在冷热水混合器和淋浴喷头之间有一根很长的管道的地方洗个澡，你就会直接体验到由于响应延迟过长而导致冷热振荡的乐趣。
How much of a delay causes what kind of oscillation under what circum- 在什么情况下，多少延迟会导致什么样的振荡？
Figure 33. The response of orders and deliveries to an increase in demand. shows the small but sharp step up in sales on day 25 and the car dealer's "perceived" sales, in which she averages the change over 3 days. shows the resulting ordering pattern, tracked by the actual deliveries from the factory. 图 33：订单和交货对需求增长的反应。 显示了第 25 天小幅但急剧上升的销售额，以及汽车经销商 "感知到的 "销售额，即她对 3 天变化的平均值。 显示了由此产生的订货模式，由工厂的实际交货量跟踪。
stances is not a simple matter. I can use this inventory system to show you why. 这不是一个简单的问题。我可以用这个库存系统来告诉你为什么。
"These oscillations are intolerable," says the car dealer (who is herself a learning system, determined now to change the behavior of the inventory system). "'I'm going to shorten the delays. There's not much I can do about the delivery delay from the factory, so I'm going to react faster myself. I'll average sales trends over only two days instead of five before I make order adjustments." "汽车经销商（她本身就是一个学习系统，现在决心改变库存系统的行为）说："这些振荡是不能容忍的。"'我要缩短延迟时间。对于工厂的交货延迟，我无能为力，所以我要自己做出更快的反应。在调整订单之前，我将只对两天而不是五天的销售趋势进行平均"。
Figure 34 illustrates what happens when the dealer's perception delay is 图 34 说明了当经销商的感知延迟为
shortened from five days to two. 从五天缩短到两天。
Not much happens when the car dealer shortens her perception delay. If anything the oscillations in the inventory of cars on the lot are a bit worse. And if, instead of shortening her perception time, the car dealer tries shortening her reaction time-making up perceived shortfalls in two days instead of three-things get very much worse, as shown in Figure 35. Something has to change and, since this system has a learning person 当汽车经销商缩短其感知延迟时，并不会发生什么。如果说有什么变化的话，那就是停车场上汽车存量的波动变得更严重了。如果汽车经销商不缩短她的感知时间，而是尝试缩短她的反应时间，将感知到的短缺时间从三天缩短到两天，情况就会变得更糟，如图 35 所示。必须有所改变，因为这个系统有一个学习者
Figure 34. The response of inventory to the same increase in demand with a shortened perception delay. 图 34.在感知延迟缩短的情况下，库存对相同需求增长的反应。
Figure 35. The response of inventory to the same increase in demand with a shortened reaction time. Acting faster makes the oscillations worse! 图 35.反应时间缩短后，库存对相同需求增长的反应。行动越快，振荡越严重！
within it, something will change. "High leverage, wrong direction," the system-thinking car dealer says to herself as she watches this failure of a policy intended to stabilize the oscillations. This perverse kind of result can be seen all the time-someone trying to fix a system is attracted intuitively to a policy lever that in fact does have a strong effect on the system. And then the well-intentioned fixer pulls the lever in the wrong direction! This is just one example of how we can be surprised by the counterintuitive behavior of systems when we start trying to change them. 在它的内部，一些东西会发生变化。"高杠杆，错误的方向，"这位具有系统思维的汽车经销商看着这项旨在稳定振荡的政策的失败，自言自语道。这种反常的结果经常出现--某个试图修复系统的人凭直觉被一个政策杠杆所吸引，而事实上，这个政策杠杆确实对系统产生了很大的影响。然后，用心良苦的修复者却把杠杆拉错了方向！这只是一个例子，说明当我们开始试图改变系统时，我们会被系统的反直觉行为吓一跳。
Part of the problem here is that the car dealer has been reacting not too slowly, but too quickly. Given the configuration of this system, she has been overreacting. Things would go better if, instead of decreasing her response delay from three days to two, she would increase the delay from three days to six, as illustrated in Figure 36. 这里的部分问题是，汽车经销商的反应不是太慢，而是太快。从这个系统的配置来看，她反应过度了。如果她不把反应延迟从三天缩短到两天，而是把延迟从三天延长到六天，情况就会好一些，如图 36 所示。
As Figure 36 shows, the oscillations are greatly damped with this change, and the system finds its new equilibrium fairly efficiently. 如图 36 所示，这种变化极大地抑制了振荡，系统相当有效地找到了新的平衡。
The most important delay in this system is the one that is not under the direct control of the car dealer. It's the delay in delivery from the Delays are pervasive in systems, factory. But even without the ability to change and they are strong determinants of behavior. Changing the length of a delay may (or may not, depending on the type of delay and the relative lengths of other delays) make a large change in the behavior of a system. that part of her system, the dealer can learn to manage inventory quite well. 在这个系统中，最重要的延迟是不受汽车经销商直接控制的延迟。这就是从工厂交货的延迟。但即使没有改变的能力，它们也是行为的有力决定因素。改变延迟时间的长短可能会（也可能不会，这取决于延迟的类型和其他延迟的相对长度）使系统的行为发生巨大变化。
Figure 36. The response of inventory to the same increase in demand with a slowed reaction time. 图 36.反应时间减慢后，库存对相同需求增长的反应。
Changing the delays in a system can make it much easier or much harder to manage. You can see why system thinkers are somewhat fanatic on the subject of delays. We're always on the alert to see where delays occur in systems, how long they are, whether they are delays in information streams or in physical processes. We can't begin to understand the dynamic behavior of systems unless we know where and how long the delays are. And we are aware that some delays can be powerful policy levers. Lengthening or shortening them can produce major changes in the behavior of systems. 改变系统中的延迟，可以使系统更容易管理，也可以使系统更难管理。你可以理解为什么系统思想家对延迟这个话题有些狂热。我们总是警惕地观察系统中出现延迟的位置、延迟的时间长短、是信息流延迟还是物理过程延迟。如果我们不知道延迟的位置和时间，就无法理解系统的动态行为。我们知道，有些延迟可以成为强有力的政策杠杆。延长或缩短延迟可以使系统行为发生重大变化。
In the big picture, one store's inventory problem may seem trivial and fixable. But imagine that the inventory is that of all the unsold automobiles in America. Orders for more or fewer cars affect production not only at assembly plants and parts factories, but also at steel mills, rubber and glass plants, textile producers, and energy producers. Everywhere in this system are perception delays, production delays, delivery delays, and construction delays. Now consider the link between car production and jobs-increased production increases the number of jobs allowing more people to buy cars. That's a reinforcing loop, which also works in the opposite directionless production, fewer jobs, fewer car sales, less production. Put in another reinforcing loop, as speculators buy and sell shares in the auto and autosupply companies based on their recent performance, so that an upsurge in production produces an upsurge in stock price, and vice versa. 从大局来看，一家商店的库存问题似乎微不足道，而且可以解决。但试想一下，这些库存是美国所有未售出汽车的库存。增加或减少汽车的订单不仅会影响装配厂和零部件厂的生产，还会影响钢铁厂、橡胶厂、玻璃厂、纺织厂和能源生产厂的生产。在这个系统中，到处都存在着观念延误、生产延误、交货延误和施工延误。现在来考虑一下汽车生产与就业之间的联系--生产的增加会增加就业岗位的数量，从而使更多的人能够购买汽车。这是一个强化循环，它的作用方向正好相反，生产减少，就业减少，汽车销售减少，生产减少。在另一个强化循环中，投机者根据汽车公司和汽车供应公司近期的业绩买卖其股票，因此产量的激增会导致股价的激增，反之亦然。
That very large system, with interconnected industries responding to each other through delays, entraining each other in their oscillations, and being amplified by multipliers and speculators, is the primary cause of business cycles. Those cycles don't come from presidents, although presidents can do much to ease or intensify the optimism of the upturns and the pain of the downturns. Economies are extremely complex systems; they are full of balancing feedback loops with delays, and they are inherently oscillatory. 这个庞大的系统，由相互关联的行业通过延迟相互响应，在振荡中相互牵制，并通过乘数和投机者放大，是商业周期的主要原因。这些周期并非来自总统，尽管总统可以在很大程度上缓解或加剧经济上行时的乐观情绪和经济下行时的痛苦。经济是一个极其复杂的系统，其中充满了平衡反馈回路和延迟，本质上是振荡的。
Two-Stock Systems 双库存系统
A Renewable Stock Constrained by a Nonrenewable Stock-an Oil Economy The systems I've displayed so far have been free of constraints imposed by their surroundings. The capital stock of the industrial economy model didn't require raw materials to produce output. The population didn't need food. The thermostat-furnace system never ran out of oil. These simple 可再生存量受制于不可再生存量--石油经济 到目前为止，我所展示的系统都没有受到周围环境的限制。工业经济模型的资本存量不需要原材料来生产产出。人口不需要食物。恒温器-火炉系统永远不会耗尽石油。这些简单的
models of the systems have been able to operate according to their unconstrained internal dynamics, so we could see what those dynamics are. 这些系统的模型能够按照其无约束的内部动态运行，因此我们可以看到这些动态是什么。
But any real physical entity is always surrounded by and exchanging things with its environment. A corporation needs a constant supply of energy and materials and workers and managers and customers. A growing corn crop needs water and nutrients and protection from pests. A population needs food and water and living space, and if it's a human population, it needs jobs and education and health care and a multitude of other things. Any entity that is using energy and processing materials needs a place to put its wastes, or a process to carry its wastes away. 但是，任何真实的实体总是被其周围的环境所包围，并与其交换着各种东西。一家公司需要源源不断的能源、材料、工人、管理人员和客户。一棵正在生长的玉米需要水和养分，还需要防止虫害。人口需要食物、水和生活空间，如果是人类，还需要工作、教育、医疗保健和其他许多东西。任何使用能源和加工材料的实体都需要一个放置废物的地方，或者一个将废物运走的过程。
Therefore, any physical, growing system is going to run into some kind of constraint, sooner or later. That constraint will take the form of a balancing loop that in some way shifts the dominance of the reinforcing loop driving the growth behavior, either by strengthening the outflow or by weakening the inflow. 因此，任何物理增长系统迟早都会遇到某种限制。这种制约会以平衡回路的形式出现，通过加强流出或削弱流入，以某种方式改变驱动增长行为的强化回路的主导地位。
Growth in a constrained environment is very common, so common that systems thinkers call it the "limits-to-growth" archetype. (We'll explore more archetypes-frequently found system structures that produce familiar behavior patterns-in Chapter Five.) Whenever we see a growing entity, whether it be a population, a corporation, a bank account, a rumor, an epidemic, or sales of a new product, we look for the reinforcing loops that are driving it and for the balancing loops that ultimately will constrain it. We know those balancing loops are there, even if they are not yet dominating the system's behavior, because no real physical system can grow forever. Even a hot new product will saturate the market eventually. A chain reaction in a nuclear power plant or bomb will run out of fuel. A virus will run out of susceptible people to infect. An economy may be constrained by physical In physical, exponentially capital or monetary capital or labor or markets or growing systems, there must be at least one reinforcing loop driving the growth and at least one balancing loop constraining the growth, because no physical system can grow forever in a finite environment. management or resources or pollution. 在受限环境中成长是非常常见的现象，以至于系统思想家称之为 "成长极限 "原型。(我们将在第五章探讨更多原型--经常发现的产生熟悉行为模式的系统结构）。每当我们看到一个不断增长的实体，无论是人口、公司、银行账户、谣言、流行病，还是新产品的销售，我们都会寻找推动其增长的强化循环，以及最终会限制其增长的平衡循环。我们知道这些平衡回路是存在的，即使它们还没有主导系统的行为，因为没有一个真实的物理系统可以永远发展下去。即使是热门的新产品，最终也会使市场饱和。核电站或炸弹的连锁反应也会耗尽燃料。病毒也会耗尽可感染的易感人群。在物理的、指数式增长的资本、货币资本、劳动力、市场或增长系统中，必须至少有一个强化环路推动增长，至少有一个平衡环路限制增长，因为没有一个物理系统可以在有限的环境中永远增长。
Like resources that supply the inflows to a stock, a pollution constraint can be renewable or nonrenewable. It's nonrenewable if the environment has no capacity to absorb the pollutant or make it harmless. It's renewable if the environment has a finite, usually variable, capacity for removal. Everything said here about resource-constrained systems, therefore, 与为存量提供流入量的资源一样，污染制约因素可以是可再生的，也可以是不可再生的。如果环境没有吸收污染物或使其无害的能力，它就是不可再生的。如果环境的清除能力是有限的，通常是可变的，那么它就是可再生的。因此，这里所说的一切都与资源受限的系统有关、
applies with the same dynamics but opposite flow directions to pollutionconstrained systems. 污染受限系统的动态相同，但流动方向相反。
The limits on a growing system may be temporary or permanent. The system may find ways to get around them for a short while or a long while, but eventually there must come some kind of accommodation, the system adjusting to the constraint, or the constraint to the system, or both to each other. In that accommodation come some interesting dynamics. 对一个不断成长的系统的限制可能是暂时的，也可能是永久的。系统可能会想办法在短时间内或长时间内绕过它们，但最终一定会出现某种调适，即系统适应限制，或限制适应系统，或两者相互适应。在这种适应过程中，会产生一些有趣的动态变化。
Whether the constraining balancing loops originate from a renewable or nonrenewable resource makes some difference, not in whether growth can continue forever, but in how growth is likely to end. 制约性平衡环路是来自可再生资源还是不可再生资源，对增长能否永远持续下去并无影响，但对增长可能如何结束却有一定影响。
Let's look, to start, at a capital system that makes its money by extracting a nonrenewable resource-say an oil company that has just discovered a huge new oil field. See Figure 37. 首先，让我们来看看一个通过开采不可再生资源来赚钱的资本系统--比如一家刚刚发现了一个巨大新油田的石油公司。见图 37。
The diagram in Figure 37 may look complicated, but it's no more than 图 37 中的图表看似复杂，其实不过是
Figure 37. Economic capital, with its reinforcing growth loop constrained by a nonrenewable resource. 图 37.经济资本，其增长循环受制于不可再生资源。
a capital-growth system like the one we've already seen, using "profit" instead of "output." Driving depreciation is the now-familiar balancing loop: the more capital stock, the more machines and refineries there are that fall apart and wear out, reducing the stock of capital. In this example, the capital stock of oil drilling and refining equipment depreciates with a 20 -year lifetime-meaning (or 5 percent) of the stock is taken out of commission each year. It builds itself up through investment of profits from oil extraction. So we see the reinforcing loop: More capital allows more resource extraction, creating more profits that can be reinvested. I've assumed that the company has a goal of 5 percent annual growth in its business capital. If there isn't enough profit for 5 percent growth, the company invests whatever profits it can. 这种资本增长体系就像我们已经看到过的，用 "利润 "代替 "产出"。推动折旧的是我们现在熟悉的平衡循环：资本存量越多，就有越多的机器和炼油厂发生故障和磨损，从而减少资本存量。在这个例子中，石油钻探和提炼设备的资本存量折旧年限为 20 年，这意味着 （或 5%）的存量每年都会停止使用。它通过投资石油开采的利润自我积累。因此，我们看到了一个不断强化的循环：更多的资本可以开采更多的资源，从而创造更多的利润用于再投资。我假定该公司的目标是业务资本每年增长 5%。如果没有足够的利润来实现 5% 的增长，公司就会将所有利润用于投资。
Profit is income minus cost. Income in this simple representation is just the price of oil times the amount of oil the company extracts. Cost is equal to capital times the operating cost (energy, labor, materials, etc.) per unit of capital. For the moment, I'll make the simplifying assumptions that both price and operating cost per unit of capital are constant. 利润是收入减去成本。在这个简单的表述中，收入只是石油价格乘以公司开采的石油量。成本等于资本乘以单位资本的运营成本（能源、劳动力、材料等）。在此，我做一个简化假设，即单位资本的价格和运营成本都是不变的。
What is not assumed to be constant is the yield of resource per unit of capital. Because this resource is not renewable, as in the case of oil, the stock feeding the extraction flow does not have an input. As the resource is extracted—as an oil well is depleted-the next barrel of oil becomes harder to get. The remaining resource is deeper down, or more dilute, or in the case of oil, under less natural pressure to force it to the surface. More and more costly and technically sophisticated measures are required to keep the resource coming. 没有假定不变的是每单位资本的资源产量。因为这种资源不是可再生的，就像石油一样，为开采流提供原料的存量没有投入。随着资源的开采--如油井枯竭--下一桶石油变得越来越难获得。剩余的资源在地下更深的地方，或者更稀薄，或者在石油的情况下，迫使其浮出地面的自然压力更小。要想继续获得资源，就必须采取成本越来越高、技术越来越复杂的措施。
Here is a new balancing feedback loop that ultimately will control the growth of capital: the more capital, the higher the extraction rate. The higher the extraction rate, the lower the resource stock. The lower the resource stock, the lower the yield of resource per unit of capital, so the lower the profit (with price assumed constant) and the lower the investment rate-therefore, the lower the rate of growth of capital. I could assume that resource depletion feeds back through operating cost as well as capital efficiency. In the real world it does both. In either case, the ensuing behavior pattern is the same-the classic dynamics of depletion (see Figure 38). 这里有一个新的平衡反馈回路，它最终将控制资本的增长：资本越多，开采率越高。开采率越高，资源存量越低。资源存量越低，每单位资本的资源产量就越低，因此利润就越低（假设价格不变），投资率就越低--因此，资本增长率就越低。我可以假设，资源损耗会通过运营成本和资本效率反馈回来。在现实世界中，两者都会产生影响。无论哪种情况，随之而来的行为模式都是一样的--典型的耗竭动态（见图 38）。
The system starts out with enough oil in the underground deposit to supply the initial scale of operation for 200 years. But, actual extraction peaks at about 40 years because of the surprising effect of exponential 系统开始时，地下储藏的石油足以满足最初 200 年的开采规模。但是，由于令人惊讶的指数效应，实际开采量在 40 年左右达到峰值。
A: Extraction rate A：提取率
B: Capital stock B: 资本存量
C: Resource stock C:资源存量
Figure 38. Extraction (A) creates profits that allow for growth of capital (B) while depleting the nonrenewable resource (C). The greater the accumulation of capital, the faster the resource is depleted. 图 38.开采（A）创造利润，使资本（B）增长，同时耗尽不可再生资源（C）。资本积累越多，资源消耗得越快。
growth in extraction. At an investment rate of 10 percent per year, the capital stock and therefore the extraction rate both grow at 5 percent per year and so double in the first 14 years. After 28 years, while the capital stock has quadrupled, extraction is starting to lag because of falling yield per unit of capital. By year 50 the cost of maintaining the capital stock has overwhelmed the income from resource extraction, so profits are no longer sufficient to keep investment ahead of depreciation. The operation quickly shuts down, as the capital stock declines. The last and most expensive of the resource stays in the ground; it doesn't pay to get it out. 开采增长。在每年 10%的投资率下，资本存量和开采率都以每年 5%的速度增长，因此在最初的 14 年中翻了一番。28 年后，虽然资本存量翻了两番，但由于单位资本产量下降，开采开始滞后。到第 50 年，维持资本存量的成本已经超过了资源开采的收入，因此利润已经不足以使投资超过折旧。随着资本存量的下降，企业很快就关闭了。最后也是最昂贵的资源留在了地下；开采出来也没有任何回报。
What happens if the original resource turns out to be twice as large as 如果原始资源的大小是
the geologists first thought-or four times as large? Of course, that makes a huge difference in the total amount of oil that can be extracted from this field. But with the continued goal of 10 percent per year reinvestment producing 5 percent per year capital growth, each doubling of the resource makes a difference of only about 14 years in the timing of the peak extraction rate, and in the lifetime of any jobs or 还是四倍之大？当然，这对该油田可开采的石油总量影响巨大。但是，如果继续以每年 10% 的再投资和每年 5% 的资本增长为目标，资源量每增加一倍，在开采量达到峰值的时间上，以及在任何工作或工作岗位的寿命上，都只会相差 14 年左右。
A quantity growing exponentially toward a constraint or limit reaches that limit in a surprisingly short time. communities dependent on the extraction industry (see Figure 39). 一个数量向一个限制或极限呈指数增长，在很短的时间内就会达到极限，依赖开采业的社区就是如此（见图 39）。
The higher and faster you grow, the farther and faster you fall, when you're building up a capital stock dependent on a nonrenewable resource. In the face of exponential growth of extraction or use, a doubling or quadrupling of the nonrenewable resource give little added time to develop alternatives. 在依赖不可再生资源建立资本存量时，增长得越高越快，下降得越远越快。在开采或使用呈指数增长的情况下，不可再生资源翻一番或翻两番，就没有多少时间来开发替代品了。
If your concern is to extract the resource and make money at the maximum possible rate, then the ultimate size of the resource is the most important number in this system. If, say, you're a worker at the mine or oil field, and your concern is with the lifetime of your job and stability of your community, then there are two important numbers: the size of the resource and the desired growth rate of capital. (Here is a good example of the goal of a feedback loop being crucial to the behavior of a system.) The real choice in the management of a nonrenewable resource is whether to get rich very fast or to get less rich but stay that way longer. 如果你关心的是以最大可能的速度开采资源并赚钱，那么资源的最终规模就是这个系统中最重要的数字。如果你是矿山或油田的工人，你关心的是工作的寿命和社区的稳定，那么就有两个重要的数字：资源的规模和期望的资本增长率。(这是一个很好的例子，说明反馈回路的目标对系统的行为至关重要）。在不可再生资源的管理中，真正的选择是快速致富，还是少富多富。
Figure 39. Extraction with two times or four times as large a resource to draw on. Each doubling of the resource makes a difference of only about fourteen years in the peak of extraction. 图 39.资源量增加两倍或四倍后的开采情况。资源量每增加一倍，开采高峰期仅相差约 14 年。
Figure 40. The peak of extraction comes much more quickly as the fraction of profits reinvested increases. 图 40.随着利润再投资比例的增加，榨取峰值来得更快。
The graph in Figure 40 shows the development of the extraction rate over time, given desired growth rates above depreciation varying from 1 percent annually, to 3 percent, 5 percent, and 7 percent. With a 7 percent growth rate, extraction of this "200-year supply" peaks within 40 years. Imagine the effects of this choice not only on the profits of the company, but on the social and natural environments of the region. 图 40 中的图表显示了开采率随时间的变化情况，在预期增长率高于折旧率的情况下，年增长率从 1%到 3%、5% 和 7%不等。如果增长率为 7%，"200 年供应量 "的开采量将在 40 年内达到峰值。试想一下，这种选择不仅会对公司的利润产生影响，还会对该地区的社会和自然环境产生影响。
Earlier I said I would make the simplifying assumption that price was constant. But what if that's not true? Suppose that in the short term the resource is so vital to consumers that a higher price won't decrease demand. In that case, as the resource gets scarce and price rises steeply, as shown in Figure 41. 前面我说过，我会做一个简化假设，即价格是不变的。但如果事实并非如此呢？假设在短期内，资源对消费者非常重要，价格上涨不会减少需求。在这种情况下，随着资源变得稀缺，价格急剧上升，如图 41 所示。
The higher price gives the industry higher profits, so investment goes up, capital stock continues rising, and the more costly remaining resources can be extracted. If you compare Figure 41 with Figure 38, where price was held constant, you can see that the main effect of rising price is to build the capital stock higher before it collapses. 价格上涨给该行业带来了更高的利润，因此投资增加，资本存量继续上升，可以开采成本更高的剩余资源。如果将图 41 与价格保持不变的图 38 进行比较，就会发现价格上涨的主要影响是在资本存量崩溃之前将其提高。
The same behavior results, by the way, if prices don't go up but if technology brings operating costs down-as has actually happened, for example, with advanced recovery techniques from oil wells, with the beneficiation process to extract low-grade taconite from exhausted iron mines, and with the cyanide leaching process that allows profitable extraction even from the tailings of gold and silver mines. 顺便说一句，如果价格不上涨，但技术降低了运营成本，也会产生同样的结果--例如，先进的油井采油技术、从枯竭的铁矿中提取低品位铁燧岩的选矿工艺，以及即使从金矿和银矿的尾矿中提取也能盈利的氰化物浸出工艺，都是如此。
A: Extraction rate A：提取率
B: Capital stock B: 资本存量
C: Resource stock C:资源存量
Figure 41. As price goes up with increasing scarcity, there is more profit to reinvest, and the capital stock can grow larger (B) driving extraction up for longer (A). The consequence is that the resource is depleted even faster at the end. 图 41.由于价格随着稀缺程度的增加而上升，因此有更多的利润可用于再投资，资本存量也会增加（B），从而使开采时间延长（A）。其结果是，资源 ，最后消耗得更快。
We all know that individual mines and fossil fuel deposits and groundwater aquifers can be depleted. There are abandoned mining towns and oil fields all over the world to testify to the reality of the behavior we've seen here. Resource companies understand this dynamic too. Well before depletion makes capital less efficient in one place, companies shift investment to discovery and development of another deposit somewhere else. But, if there are local limits, eventually will there be global ones? 我们都知道，个别矿山、化石燃料矿藏和地下蓄水层可能会枯竭。世界各地都有废弃的矿镇和油田，证明了我们在这里看到的行为的真实性。资源公司也了解这种动态。早在资源枯竭导致一个地方的资本效率降低之前，公司就会将投资转向在其他地方发现和开发另一个矿藏。但是，如果有地方限制，最终会不会有全球限制呢？
I'll leave you to have this argument with yourself, or with someone of the 我让你自己去争论吧，或者去和某个人争论。
opposite persuasion. I will just point out that, according to the dynamics of depletion, the larger the stock of initial resources, the more new discoveries, the longer the growth loops elude the control loops, and the higher the capital stock and its extraction rate grow, and the earlier, faster, and farther will be the economic fall on the back side of the production peak. 我只想指出，根据耗竭动力学，初始资源存量越大，新发现越多，增长环路逃避控制环路的时间越长，资本存量越高。我只想指出，根据耗竭的动力学原理，初始资源存量越大，新发现越多，增长环路逃避控制环路的时间越长，资本存量及其开采率增长得越高，生产峰值背面的经济衰退就会越早、越快、越远。
Unless, perhaps, the economy can learn to operate entirely from renewable resources. 也许，除非经济能够学会完全依靠可再生资源运行。
Renewable Stock Constrained by a Renewable Stock-a Fishing Economy 受可再生资源制约的可再生资源--渔业经济
Assume the same capital system as before, except that now there is an inflow to the resource stock, making it renewable. The renewable resource in this system could be fish and the capital stock could be fishing boats. It also could be trees and sawmills, or pasture and cows. Living renewable resources such as fish or trees or grass can regenerate themselves from themselves with a reinforcing feedback loop. Nonliving renewable resources such as sunlight or wind or water in a river are regenerated not through a reinforcing loop, but through a steady input that keeps refilling the resource stock no matter what the current state of that stock might be. This same "renewable resource system" structure occurs in an epidemic of a cold virus. It spares its victims who are then able to catch another cold. Sales of a product people need to buy regularly is also a renewable resource system; the stock of potential customers is ever regenerated. Likewise an insect infestation that destroys part but not all of a plant; the plant can regenerate and the insect can eat more. In all these cases, there is an input that keeps refilling the constraining resource stock (as shown in Figure 42).
We will use the example of a fishery. Once again, assume that the lifetime of capital is 20 years and the industry will grow, if it can, at 5 percent per year. As with the nonrenewable resource, assume that as the resource gets scarce it costs more, in terms of capital, to harvest it. Bigger fishing boats that can go longer distances and are equipped with sonar are needed to find the last schools of fish. Or miles-long drift nets are needed to catch them. Or on-board refrigeration systems are needed to bring them back to port from longer distances. All this takes more capital. 我们以渔业为例。再次假设资本的寿命为 20 年，如果可以的话，该行业将以每年 5%的速度增长。与不可再生资源一样，假设随着资源的稀缺，捕捞的资本成本也会增加。要想找到最后的鱼群，就需要更大的渔船、更远的航程和声纳设备。或者需要数英里长的流网来捕捞。或者需要船载制冷系统，以便从更远的地方将鱼运回港口。所有这些都需要更多的资金。
The regeneration rate of the fish is not constant, but is dependent on the number of fish in the area-fish density. If the fish are very dense, their reproduction rate is near zero, limited by available food and habitat. If the fish population falls a bit, it can regenerate at a faster and faster rate, 鱼类的再生率并非恒定不变，而是取决于该区域的鱼类数量--鱼类密度。如果鱼群非常密集，受可用食物和栖息地的限制，它们的繁殖率接近于零。如果鱼的数量稍有减少，其再生速度就会越来越快、
Figure 42. Economic capital with its reinforcing growth loop constrained by a renewable resource. 图 42.受可再生资源制约的经济资本及其强化增长循环。
because it can take advantage of unused nutrients or space in the ecosystem. But at some point the fish reproduction rate reaches its maximum. If the population is further depleted, it breeds not faster and faster, but slower and slower. That's because the fish can't find each other, or because another species has moved into its niche. 因为它可以利用生态系统中闲置的养分或空间。但是，鱼类的繁殖率在某些时候会达到最大值。如果种群数量进一步减少，它的繁殖速度不是越来越快，而是越来越慢。这是因为鱼类找不到彼此，或者是因为另一个物种进入了它的生态位。
This simplified model of a fishery economy is affected by three nonlinear relationships: price (scarcer fish are more expensive); regeneration rate (scarcer fish don't breed much, nor do crowded fish); and yield per unit of capital (efficiency of the fishing technology and practices). 这个简化的渔业经济模型受到三个非线性关系的影响：价格（稀缺的鱼更贵）；再生率（稀缺的鱼不常繁殖，拥挤的鱼也不常繁殖）；单位资本产量（捕鱼技术和做法的效率）。
This system can produce many different sets of behaviors. Figure 43 shows one of them. 这个系统可以产生许多不同的行为。图 43 展示了其中一种。
In Figure 43, we see capital and fish harvest rise exponentially at first. 在图 43 中，我们可以看到资本和渔获量起初呈指数增长。
The fish population (the resource stock) falls, but that stimulates the fish reproduction rate. For decades the resource can go on supplying an exponentially increasing harvest rate. Eventually, the harvest rises too far and the fish population falls low enough to reduce the profitability of the fishing fleet. The balancing feedback of falling harvest reducing profits brings 鱼类数量（资源量）下降，但这刺激了鱼类的繁殖率。几十年来，这种资源的捕获量一直呈指数增长。最终，捕捞量上升过快，鱼群数量下降到足以降低捕鱼船队的盈利能力。捕捞量减少利润降低的平衡反馈带来了
B: Capital stock B: 资本存量
C: Resource stock C:资源存量
Figure 43. Annual harvest creates profits that allow for growth of capital stock (B), but the harvest levels off, after a small overshoot in this case. The result of leveling harvest is that the resource stock (C) also stabilizes. 图 43.年收获量 创造的利润使资本存量（B）得以增长，但收获量在小幅超调后趋于平稳。收成持平的结果是资源存量（C）也趋于稳定。
down the investment rate quickly enough to bring the fishing fleet into equilibrium with the fish resource. The fleet can't grow forever, but it can maintain a high and steady harvest rate forever. 投资率迅速下降，足以使捕鱼船队与鱼类资源达到平衡。渔船队不可能永远增长，但它可以永远保持稳定的高捕获率。
Just a minor change in the strength of the controlling balancing feedback loop through yield per unit of capital, however, can make a surpris- 然而，通过单位资本收益率控制平衡反馈回路的强度只要发生微小变化，就会产生令人吃惊的结果。
B: Capital stock B: 资本存量
C: Resource stock C:资源存量
Figure 44. A slight increase in yield per unit of capital-increasingly efficient technology in this case-creates a pattern of overshoot and oscillation around a stable value in the harvest rate , the stock of economic capital (B), and in the resource stock. 图 44.单位资本产量的轻微增加--在这种情况下，技术效率不断提高--会在收获率 、经济资本存量（B）和资源存量的稳定值附近产生超调和振荡模式。
A: Harvest rate A: 收获率
B: Capital stock B: 资本存量
C: Resource stock C:资源存量
Figure 45. An even greater increase in yield per unit of capital creates a patterns of overshoot and collapse in the harvest (A), the economic capital (B), and the resource (C). 图 45.每单位资本产量的更大增长会导致收成（A）、经济资本（B）和资源（C）的超调和崩溃。
ing difference. Suppose that in an attempt to raise the catch in the fishery, the industry comes up with a technology to improve the efficiency of the boats (sonar, for example, to find the scarcer fish). As the fish population declines, the fleet's ability to pull in the same catch per boat is maintained just a little longer (see Figure 44). 这就是区别。假设为了提高渔获量，该行业想出了一种提高渔船效率的技术（例如声纳，用来寻找稀少的鱼）。随着鱼群数量的减少，船队每艘船的渔获量保持不变的时间会更长一些（见图 44）。
Figure 44 shows another case of high leverage, wrong direction! This 图 44 显示了另一个高杠杆、方向错误的案例！这
technical change, which increases the productivity of all fishermen, throws the system into instability. Oscillations appear! 技术变革提高了所有渔民的生产率，使整个系统陷入不稳定。振荡出现了！
If the fishing technology gets even better, the boats can go on operating economically even at very low fish densities. The result can be a nearly complete wipeout both of the fish and of the fishing industry. The consequence is the marine equivalent of desertification. The fish have been turned, for all practical purposes, into a nonrenewable resource. Figure 45 illustrates this scenario. 如果捕鱼技术更上一层楼，即使在鱼群密度很低的情况下，渔船也能继续经济地作业。结果可能是鱼类和捕鱼业几乎全军覆没。其后果相当于海洋沙漠化。实际上，鱼类已经变成了不可再生资源。图 45 展示了这种情况。
In many real economies based on real renewable resources-as opposed to this simple model-the very small surviving population retains the potential to build its numbers back up again, once the capital driving the harvest is gone. The whole pattern is repeated, decades later. Very long-term renewable-resource cycles like these have been observed, for example, in the logging industry in New England, now in its third cycle of growth, overcutting, collapse, and eventual regeneration of the resource. But this is not true for all resource populations. More and more, increases in technology and harvest efficiency have the ability to drive resource populations to extinction. 在许多以真正的可再生资源为基础的实际经济中--与这种简单的模式不同--一旦推动收获的资本消失，幸存的极少数人口仍有可能再次增加其数量。整个模式会在几十年后重演。例如，在新英格兰的伐木业中就可以观察到类似这样的长期可再生资源循环，现在已经进入了资源增长、过度砍伐、崩溃和最终再生的第三个循环。但并非所有的资源种群都是如此。越来越多的技术和采伐效率的提高有能力将资源种群推向灭绝。
Whether a real renewable resource system can survive overharvest depends on what happens to it during the time when the resource is severely depleted. A very small fish population may become especially vulnerable to pollution or storms or lack of genetic diversity. If this is a forest or grassland resource, the exposed soils may be vulnerable to erosion. Or the nearly empty ecological niche may be filled in by a competitor. Or perhaps the depleted resource can survive and rebuild itself again. 一个真正的可再生资源系统能否经受住过度捕捞，取决于在资源严重枯竭时会发生什么情况。数量极少的鱼类可能特别容易受到污染、风暴或缺乏遗传多样性的影响。如果是森林或草原资源，裸露的土壤可能容易受到侵蚀。或者，几乎空白的生态位可能会被竞争者填补。又或者，枯竭的资源可以存活下来并再次重建。
I've shown three sets of possible behaviors of this renewable resource system here: 我在这里展示了这种可再生资源系统的三组可能行为：
overshoot and adjustment to a sustainable equilibrium, 过冲和调整到可持续的平衡状态、
overshoot beyond that equilibrium followed by oscillation around it, and 超过平衡点，然后在平衡点附近振荡，以及
overshoot followed by collapse of the resource and the industry dependent on the resource. 资源和依赖该资源的产业随之崩溃。
Which outcome actually occurs depends on two things. The first is the critical threshold beyond which the resource population's ability to regenerate itself is damaged. The second is the rapidity and effectiveness of the balancing feedback loop that slows capital growth as the resource becomes depleted. If the feedback is fast enough to stop capital growth before the critical threshold is reached, the whole system comes smoothly into equilibrium. If the balancing feedback is slower and less effective, the system oscillates. If the balancing loop is very weak, so that capital can go on growing even as the resource is reduced below its threshold ability to regenerate itself, the resource and the industry both collapse. 实际出现哪种结果取决于两点。首先是临界值，超过这个临界值，资源群体的自我再生能力就会受到损害。其次是平衡反馈回路的速度和有效性，该回路会随着资源的耗竭而减缓资本的增长。如果反馈足够快，能够在达到临界阈值之前阻止资本增长，那么整个系统就会顺利进入平衡状态。如果平衡反馈较慢，效果较差，系统就会振荡。如果平衡回路非常弱，以至于即使资源减少到低于其自我再生能力的临界值，资本仍能继续增长，那么资源和产业都会崩溃。
Neither renewable nor nonrenewable limits to growth allow a physical stock to grow forever, but the constraints they impose are dynamically quite different. The difference comes because of the difference between stocks and flows. 无论是可再生还是不可再生的增长限制，都不允许实物存量永远增长，但它们所施加的限制在动态上却截然不同。这种差异来自于存量和流量的不同。
The trick, as with all the behavioral possibilities of complex systems, is to recognize what structures contain which latent behaviors, and what conditions release those behaviors-and, where possible, to arrange the structures and conditions to reduce the probability of destructive behaviors and to encourage the possibility of beneficial ones. 与复杂系统的所有行为可能性一样，诀窍在于识别哪些结构包含哪些潜在行为，以及哪些条件可以释放这些行为--并在可能的情况下，安排这些结构和条件，以降低破坏性行为的可能性，并鼓励有益行为的可能性。
PART TWO 第二部分
Systems and Us 系统与我们
Why Systems Work So Well 系统为何如此有效
If the land mechanism as a whole is good, then every part is good, whether we understand it or not. If the biota, in the course of aeons, has built something we like but do not understand, then who but a fool would discard seemingly useless parts? To keep every cog and wheel is the first precaution of intelligent tinkering. 如果土地机制作为一个整体是好的，那么每个部分都是好的，无论我们是否理解它。如果生物群在漫长的岁月中创造出了我们喜欢但不理解的东西，那么除了傻瓜，谁会丢弃看似无用的部分呢？保留每一个齿轮和轮子，是智能修补的首要预防措施。
—Aldo Leopold, forester -奥尔多-利奥波德， 林务员
Chapter Two introduced simple systems that create their own behavior based on their structures. Some are quite elegant-surviving the buffeting of the world—and, within limits, regaining their composure and proceeding on about their business of maintaining a room's temperature, depleting an oil field, or bringing into balance the size of a fishing fleet with the productivity of a fishery resource. 第二章介绍了一些简单的系统，它们根据自身的结构创造自己的行为。有些系统相当优雅--经受住了世界的冲击，并在一定范围内恢复平静，继续维持房间温度、耗尽油田或使捕鱼船队的规模与渔业资源的生产力达到平衡。
If pushed too far, systems may well fall apart or exhibit heretofore unobserved behavior. But, by and large, they manage quite well. And that is the beauty of systems: They can work so well. When systems work well, we see a kind of harmony in their functioning. Think of a community kicking in to high gear to respond to a storm. People work long hours to help victims, talents and skills emerge; once the emergency is over, life goes back to "normal." 如果逼得太紧，系统很可能会崩溃，或者表现出前所未见的行为。但总的来说，它们都能处理得很好。这就是系统的魅力所在：它们可以运行得如此之好。当系统运行良好时，我们会看到其运作中的一种和谐。想一想社区为应对暴风雨而全力以赴的情景。人们长时间工作以帮助灾民，人才和技能不断涌现；一旦紧急情况结束，生活就会恢复 "正常"。
Why do systems work so well? Consider the properties of highly functional systems-machines or human communities or ecosystems-which are familiar to you. Chances are good that you may have observed one of three characteristics: resilience, self-organization, or hierarchy. 为什么系统运转如此良好？想想你所熟悉的高功能系统--机器、人类社区或生态系统--的特性。你很有可能观察到以下三个特征中的一个：复原力、自组织或层次结构。
Resilience 复原力
Placing a system in a straitjacket of constancy can cause fragility to evolve. 将一个系统置于恒定的束缚中会导致脆弱性的发展。
C. S. Holling, 2 ecologist C.S. 霍林，2 位生态学家
Resilience has many definitions, depending on the branch of engineering, ecology, or system science doing the defining. For our purposes, the normal dictionary meaning will do: "the ability to bounce or spring back into shape, position, etc., after being pressed or stretched. Elasticity. The ability to recover strength, spirits, good humor, or any other aspect quickly." Resilience is a measure of a system's ability to survive and persist within a variable environment. The opposite of resilience is brittleness or rigidity. 复原力有很多定义，取决于工程学、生态学或系统科学的不同分支。就我们的目的而言，字典中的一般含义即可："受压或拉伸后反弹或弹回形状、位置等的能力。弹性。迅速恢复体力、精神、幽默感或其他方面的能力"。复原力是衡量一个系统在多变环境中生存和坚持的能力。与弹性相反的是脆性或刚性。
Resilience arises from a rich structure of many feedback loops that can work in different ways to restore a system even after a large perturbation. A single balancing loop brings a system stock back to its desired state. Resilience is provided by several such loops, operating through different mechanisms, at different time scales, and with redundancy—one kicking in if another one fails. 复原力源于由许多反馈回路组成的丰富结构，这些反馈回路可以以不同的方式发挥作用，即使在受到巨大扰动后也能恢复系统。单一的平衡回路会使系统恢复到理想状态。复原力是由多个这样的回路提供的，它们通过不同的机制、在不同的时间尺度上运行，并具有冗余性--一个回路在另一个回路失效时发挥作用。
A set of feedback loops that can restore or rebuild feedback loops is resilience at a still higher level—meta-resilience, if you will. Even higher metameta-resilience comes from feedback loops that can learn, create, design, and evolve ever more complex restorative structures. Systems that can do this are self-organizing, which will be the next surprising system characteristic I come to. 一套能够恢复或重建反馈回路的反馈回路就是更高层次的复原力--元复原力。更高层次的元复原力来自于能够学习、创造、设计和演化出更加复杂的复原结构的反馈回路。能够做到这一点的系统就是自组织系统，这将是我要谈到的下一个令人惊讶的系统特征。
The human body is an astonishing example of a resilient system. It can fend off thousands of different kinds of invaders, it can tolerate wide ranges of temperature and wide variations in food supply, it can reallocate blood supply, repair rips, gear up or slow down metabo- 人体是复原力惊人的系统。它能抵御成千上万种不同的入侵者，它能忍受大范围的温度变化和食物供应的巨大变化，它能重新分配血液供应、修复裂痕、加快或减慢新陈代谢------这一切都源于它对人体的适应能力。
There are always limits to resilience. lism, and compensate to some extent for missing or defective parts. Add to it a self-organizing intelligence that can learn, socialize, design technologies, and even transplant body parts, and you have a formidably resilient system-although not infinitely so, because, so far at least, no human body-plus-intelligence has been resilient enough to keep itself or any other body from eventually dying. 复原力总是有限的。再加上一个能够学习、社交、设计技术甚至移植身体器官的自组织智能体，你就拥有了一个强大的复原力系统--尽管不是无限的，因为至少到目前为止，还没有一个人类身体加智能体的复原力足以让自己或任何其他身体最终免于死亡。
Ecosystems are also remarkably resilient, with multiple species hold- 生态系统的复原力也非常强，多个物种可保持
ing each other in check, moving around in space, multiplying or declining over time in response to weather and the availability of nutrients and the impacts of human activities. Populations and ecosystems also have the ability to "learn" and evolve through their incredibly rich genetic variability. They can, given enough time, come up with whole new systems to take advantage of changing opportunities for life support. 随着时间的推移，种群和生态系统会随着天气、营养物质的供应以及人类活动的影响而相互制约、在空间中移动、繁殖或衰退。种群和生态系统还具有 "学习 "能力，并通过其极其丰富的基因变异性不断进化。只要有足够的时间，它们就能创造出全新的系统，利用不断变化的机会维持生命。
Resilience is not the same thing as being static or constant over time. Resilient systems can be very dynamic. Short-term oscillations, or periodic outbreaks, or long cycles of succession, climax, and collapse may in fact be the normal condition, which resilience acts to restore! 复原力并不等同于静态或长期不变。具有复原力的系统可以是非常动态的。短期振荡、周期性爆发或长期的演替、高潮和崩溃周期实际上都可能是正常状态，而复原力的作用就是恢复这种正常状态！
And, conversely, systems that are constant over time can be unresilient. This distinction between static stability and resilience is important. Static stability is something you can see; it's measured by variation in the condition of a system week by week or year by year. Resilience is something that may be very hard to see, unless you exceed its limits, overwhelm and damage the balancing loops, and the system structure breaks down. Because resilience may not be obvious without a whole-system view, people often sacrifice resilience for stability, or for productivity, or for some other more immediately recognizable system property. 反之，随着时间推移而保持不变的系统也可能缺乏复原力。静态稳定性和复原力之间的区别非常重要。静态稳定性是可以看得见的；它是通过系统每周或每年的状况变化来衡量的。而恢复力则很难察觉，除非你超过了它的极限，使平衡回路不堪重负并受到破坏，系统结构崩溃。因为如果不从整个系统的角度来看，复原力可能并不明显，所以人们往往会牺牲复原力来换取稳定性、生产率或其他一些更容易识别的系统特性。
Injections of genetically engineered bovine growth hormone increase the milk production of a cow without proportionately increasing the cow's food intake. The hormone diverts some of the cow's metabolic energy from other bodily functions to milk production. (Cattle breeding over centuries has done much the same thing but not to the same degree.) The cost of increased production is lowered resilience. The cow is less healthy, less long-lived, more dependent on human management. 注射基因工程牛生长激素可提高奶牛的产奶量，而不会相应增加奶牛的进食量。这种激素将奶牛的部分新陈代谢能量从其他身体功能转移到牛奶生产上。(几个世纪以来，牛的育种也做了同样的事情，但程度不同）。提高产量的代价是降低复原力。奶牛的健康程度降低，寿命缩短，更加依赖人类的管理。
Just-in-time deliveries of products to retailers or parts to manufacturers have reduced inventory instabilities and brought down costs in many industries. The just-in-time model also has made the production system more vulnerable, however, to perturbations in fuel supply, traffic flow, computer breakdown, labor availability, and other possible glitches. 向零售商及时交付产品或向制造商及时交付零部件，减少了许多行业的库存不稳定性，降低了成本。然而，准时交货模式也使生产系统更容易受到燃料供应、交通流量、计算机故障、劳动力可用性和其他可能出现的故障的影响。
Hundreds of years of intensive management of the forests of Europe gradually have replaced native ecosystems with singleage, single-species plantations, often of nonnative trees. These 欧洲森林经过数百年的密集管理，逐渐被单一树龄、单一树种的种植园取代，这些种植园通常种植的是非本地树木。这些
forests are designed to yield wood and pulp at a high rate indefinitely. However, without multiple species interacting with each other and drawing and returning varying combinations of nutrients from the soil, these forests have lost their resilience. They seem to be especially vulnerable to a new form of insult: industrial air pollution. 森林的目的是无限期地大量生产木材和纸浆。然而，如果没有多个物种之间的相互作用，没有从土壤中汲取和返回不同组合的养分，这些森林就失去了它们的复原力。它们似乎特别容易受到一种新形式的侮辱：工业空气污染。
Many chronic diseases, such as cancer and heart disease, come from breakdown of resilience mechanisms that repair DNA, keep blood vessels flexible, or control cell division. Ecological disasters in many places come from loss of resilience, as species are removed from ecosystems, soil chemistry and biology are disturbed, or toxins build up. Large organizations of all kinds, from corporations to governments, lose their resilience simply because the feedback mechanisms by which they sense and respond to their environment have to travel through too many layers of delay and distortion. (More on that in a minute, when we come to hierarchies.) 许多慢性疾病，如癌症和心脏病，都是由于修复 DNA、保持血管弹性或控制细胞分裂的复原机制遭到破坏所致。许多地方的生态灾难都源于复原力的丧失，因为生态系统中的物种被移除，土壤化学和生物学受到干扰，或者毒素积聚。从企业到政府，各种大型组织都会丧失其复原力，原因很简单，因为它们感知和响应环境的反馈机制必须经过太多的延迟和扭曲。(关于这一点，我们稍后将讨论等级制度）。
I think of resilience as a plateau upon which the system can play, performing its normal functions in safety. A resilient system has a big plateau, a lot of space over which it can wander, with gentle, elastic walls that will bounce it back, if it comes near a dangerous edge. 我认为弹性是一个高原，系统可以在这个高原上安全地发挥正常功能。一个有弹性的系统有一个很大的高原，有很大的空间供它徜徉，如果它接近危险的边缘，会有温和而有弹性的墙壁把它弹回来。
Systems need to be managed not only for productivity or stability, they also need to be managed for resiliencethe ability to recover from perturbation, the ability to restore or repair themselves. 对系统进行管理，不仅是为了提高生产率或稳定性，还需要对其进行恢复性管理，即从干扰中恢复的能力，自我恢复或修复的能力。
As a system loses its resilience, its plateau shrinks, and its protective walls become lower and more rigid, until the system is operating on a knifeedge, likely to fall off in one direction or another whenever it makes a move. Loss of resilience can come as a surprise, because the system usually is paying much more attention to its play than to its playing space. One day it does something it has done a hundred times before and crashes. 当一个系统失去弹性时，它的高原就会缩小，它的保护墙就会变得越来越低，越来越僵硬，直到系统在刀刃上运行，只要它一动，就有可能向这个或那个方向掉下去。恢复能力的丧失可能会让人大吃一惊，因为系统通常更关注它的游戏，而不是它的游戏空间。有一天，它做了一件已经做了上百次的事情，结果崩溃了。
Awareness of resilience enables one to see many ways to preserve or enhance a system's own restorative powers. That awareness is behind the encouragement of natural ecosystems on farms, so that predators can take on more of the job of controlling pests. It is behind "holistic" health care that tries not only to cure disease but also to build up a body's internal resistance. It is behind aid programs that do more than give food or money-that try to change the circumstances that obstruct peoples' ability to provide their own food or money. 对恢复力的认识使人们能够看到许多保护或增强系统自身恢复力的方法。这种意识的背后是对农场自然生态系统的鼓励，这样捕食者就可以承担更多控制害虫的工作。这就是 "整体 "保健的背后，它不仅试图治疗疾病，还试图增强人体的内部抵抗力。援助计划不仅仅是提供食物或金钱，而是试图改变阻碍人们自己提供食物或金钱的环境。
Self-Organization 自我组织
[Evolution] appears to be not a series of accidents the course of which is determined only by the change of environments during earth history and the resulting struggle for existence, . . . but is governed by definite laws. . . . The discovery of these laws constitutes one of the most important tasks of the future. [进化]似乎并不是一系列的偶然事件，其过程仅仅是由地球历史上环境的变化和由此产生的生存斗争决定的，......而是受明确规律支配的。. . .发现这些规律是未来最重要的任务之一。
—Ludwig von Bertalanffy, biologist 路德维希-冯-贝尔塔兰菲， 生物学家
The most marvelous characteristic of some complex systems is their ability to learn, diversify, complexify, evolve. It is the ability of a single fertilized ovum to generate, out of itself, the incredible complexity of a mature frog, or chicken, or person. It is the ability of nature to have diversified millions of fantastic species out of a puddle of organic chemicals. It is the ability of a society to take the ideas of burning coal, making steam, pumping water, and specializing labor, and develop them eventually into an automobile assembly plant, a city of skyscrapers, a worldwide network of communications. 一些复杂系统最令人惊叹的特点是它们具有学习、多样化、复杂化和进化的能力。这就是一个受精卵能够从自身产生成熟的青蛙、鸡或人这种令人难以置信的复杂性的能力。大自然有能力从一滩有机化学物质中分化出数百万个奇妙的物种。一个社会有能力把烧煤、制造蒸汽、抽水和专业化劳动的想法，最终发展成汽车装配厂、摩天大楼林立的城市和遍布全球的通信网络。
This capacity of a system to make its own structure more complex is called self-organization. You see self-organization in a small, mechanistic way whenever you see a snowflake, or ice feathers on a poorly insulated window, or a supersaturated solution suddenly forming a garden of crystals. You see self-organization in a more profound way whenever a seed sprouts, or a baby learns to speak, or a neighborhood decides to come together to oppose a toxic waste dump. 系统使自身结构变得更加复杂的这种能力被称为自组织。每当你看到一片雪花，或隔热性能很差的窗户上出现冰羽，或过饱和溶液突然形成一个晶体花园时，你就会以一种微小的、机械的方式看到自组织。每当一粒种子萌发，或一个婴儿学会说话，或一个社区决定联合起来反对有毒废物倾倒时，你就会以一种更深刻的方式看到自组织。
Self-organization is such a common property, particularly of living systems, that we take it for granted. If we didn't, we would be dazzled by the unfolding systems of our world. And if we weren't nearly blind to the property of self-organization, we would do better at encouraging, rather than destroying, the self-organizing capacities of the systems of which we are a part. 自组织是一种常见的特性，尤其是在生命系统中，我们认为这是理所当然的。否则，我们就会被世界上不断发展的系统弄得眼花缭乱。如果我们不是对自组织的特性视而不见，我们就会更好地鼓励而不是破坏我们所在系统的自组织能力。
Like resilience, self-organization is often sacrificed for purposes of short-term productivity and stability. Productivity and stability are the usual excuses for turning creative human beings into mechanical adjuncts to production processes. Or for narrowing the genetic variability of crop plants. Or for establishing bureaucracies and theories of knowledge that treat people as if they were only numbers. 与复原力一样，自组织也常常为了短期的生产率和稳定性而被牺牲。生产力和稳定性通常是把有创造力的人类变成生产流程的机械附属品的借口。或者是缩小农作物的基因变异性。或者是为了建立官僚机构和知识理论，把人当作数字看待。
Self-organization produces heterogeneity and unpredictability. It is likely 自组织产生异质性和不可预测性。很可能
to come up with whole new structures, whole new ways of doing things. It requires freedom and experimentation, and a certain amount of disorder. These conditions that encourage self-organization often can be scary for individuals and threatening to power structures. As a consequence, education systems may restrict the creative powers of children instead of stimulating those powers. Economic policies may lean toward supporting established, powerful enterprises rather than upstart, new ones. And many governments prefer their people not to be too self-organizing. 要想出全新的结构、全新的做事方法。这需要自由和实验，也需要一定程度的无序。这些鼓励自我组织的条件往往会让个人感到恐惧，并对权力结构构成威胁。因此，教育系统可能会限制而不是激发儿童的创造力。经济政策可能会倾向于支持已有的、强大的企业，而不是后起的新企业。许多国家的政府也不希望人民过于自我组织。
Fortunately, self-organization is such a basic property of living systems that even the most overbearing power structure can never fully kill it, although in the name of law and order, self-organization can be suppressed for long, barren, cruel, boring periods. 幸运的是，自组织是生命系统的基本属性，即使是最霸道的权力结构也无法完全扼杀它，尽管在法律和秩序的名义下，自组织可以被长期压制，荒芜、残酷、无聊。
Systems theorists used to think that self-organization was such a complex property of systems that it could never be understood. Computers were used to model mechanistic, "deterministic" systems, not evolutionary ones, because it was suspected, without much thought, that evolutionary systems were simply not understandable. 系统理论学家曾经认为，自组织是系统的一个复杂属性，永远无法理解。计算机被用来模拟机械的、"确定性 "的系统，而不是进化系统，因为人们不假思索地怀疑，进化系统根本无法理解。
New discoveries, however, suggest that just a few simple organizing principles can lead to wildly diverse self-organizing structures. Imagine a triangle with three equal sides. Add to the middle of each side another equilateral triangle, one-third the size of the first one. Add to each of the new sides another triangle, one-third smaller. And so on. The result is called a Koch snowflake. (See Figure 46.) Its edge has tremendous length—but it can be contained within a circle. This structure is one simple example of fractal geometry-a realm of mathematics and art populated by elaborate shapes formed by relatively simple rules. 然而，新的发现表明，只需几个简单的组织原则，就能产生种类繁多的自组织结构。想象一个三边相等的三角形。在每条边的中间再加上一个等边三角形，大小是第一个三角形的三分之一。在每条新边的中间再加上一个三角形，比第一个三角形小三分之一。以此类推。它的边长非常大，但可以包含在一个圆内。这种结构是分形几何的一个简单例子--在数学和艺术领域中，由相对简单的规则形成的形状非常复杂。
Similarly, the delicate, beautiful, intricate structure of a stylized fern can be generated by a computer with just a few simple fractal rules. The 同样，计算机只需使用几条简单的分形规则，就能生成造型蕨类植物精致、美丽、复杂的结构。分形
Figure 46. Even a delicate and intricate pattern, such as the Koch snowflake shown here, can evolve from a simple set of organizing principles or decision rules. 图 46.即使是精致复杂的图案，如图中的科赫雪花，也可以从一套简单的组织原则或决策规则演变而来。
differentiation of a single cell into a human being probably proceeds by some similar set of geometric rules, basically simple, but generating utter complexity. (It is because of fractal geometry that the average human lung has enough surface area to cover a tennis court.) 从一个细胞分化成一个人，可能也是按照类似的几何规则进行的，这些规则基本上很简单，但却非常复杂。(正是由于分形几何，人类肺部的平均表面积足以覆盖一个网球场）。
Here are some other examples of simple organizing rules that have led to self-organizing systems of great complexity: 下面还有一些简单的组织规则，却导致了非常复杂的自组织系统的例子：
All of life, from viruses to redwood trees, from amoebas to elephants, is based on the basic organizing rules encapsulated in the chemistry of DNA, RNA, and protein molecules. 所有的生命，从病毒到红杉树，从变形虫到大象，都是基于 DNA、RNA 和蛋白质分子化学所包含的基本组织规则。
The agricultural revolution and all that followed started with the simple, shocking ideas that people could stay settled in one place, own land, select and cultivate crops. 农业革命及其后的一切都始于一个简单而令人震惊的想法，即人们可以在一个地方定居下来，拥有土地，选择并种植农作物。
-"God created the universe with the earth at its center, the land with the castle at its center, and humanity with the Church at its center"-the organizing principle for the elaborate social and physical structures of Europe in the Middle Ages. 上帝以地球为中心创造了宇宙，以城堡为中心创造了大地，以教会为中心创造了人类"--这是中世纪欧洲繁复的社会和物质结构的组织原则。
-"God and morality are outmoded ideas; people should be objective and scientific, should own and multiply the means of production, and should treat people and nature as instrumental inputs to production"-the organizing principles of the Industrial Revolution. -"上帝和道德都是过时的观念；人们应该客观和科学，应该拥有和增殖生产资料，应该把人和自然当作生产的工具性投入"-这是工业革命的组织原则。
Out of simple rules of self-organization can grow enormous, diversifying crystals of technology, physical structures, organizations, and cultures. 从简单的自组织规则中，可以生长出巨大的、多样化的技术、物理结构、组织和文化晶体。
Science knows now that self-organizing systems can arise from simple rules. Science, itself a self-organizing system, likes to think that all the complexity of the world must arise, ultimately, from simple rules. Whether that actually happens is something that science does not yet know. 科学现在知道，自组织系统可以从简单规则中产生。科学本身就是一个自组织系统，它喜欢认为世界上所有的复杂性最终都必须产生于简单的规则。至于这是否真的会发生，科学还不得而知。
Systems often have the property of self-organization-the ability to structure themselves, to create new structure, to learn, diversify, and complexify. Even complex forms of self-organization may arise from relatively simple organizing rules-or may not. 系统通常具有自组织的特性--能够自我组织、创造新的结构、学习、多样化和复杂化。即使是复杂的自组织形式，也可能源于相对简单的组织规则，也可能不是。
hone our abilities to understand parts, 磨练我们理解部件的能力、
"Definitions of words in bold face can be found in the Glossary. "粗体字的定义见术语表。
