Editorial 社论

Available online 24 May 2018
2018 年 5 月 24 日在线提供

© 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).
© 2018 作者。由 Elsevier Ltd. 出版这是一篇在 CC BY 许可 （http:// creativecommons.org/licenses/by/4.0/） 下的开放获取文章。

Whether the sector of growth matters for the speed of poverty reduction, and why, has been the topic of intense study and debate. The debate was especially lively during the 1990s and 2000s, in the run-up to the 2008 world food price crisis. With the adoption of the Millennium Development Goals, the world had shifted its focus to poverty reduction, world food prices had been on a three-decade downward trend, and agriculture was no longer considered so critical to poverty-reduction efforts as during the 1960s and 1970s (Johnston & Mellor, 1961; Timmer, 2010). At the same time, and drawing on recent history, a growing number of empirical studies confirmed nonetheless that growth in agriculture had been more effective in reducing poverty over the past decades than growth outside agriculture. ${}^1$${}^1$^(1){ }^{1}
增长部门是否对减贫的速度很重要，以及为什么，一直是激烈研究和辩论的话题。在 1990 年代和 2000 年代，也就是 2008 年世界食品价格危机的准备阶段，这场辩论尤其激烈。随着千年发展目标的通过，世界已将重点转移到减贫上，世界食品价格已经处于三十年的下降趋势，农业不再像1960年代和1970年代那样被认为对减贫努力如此重要（Johnston & Mellor，1961;Timmer，2010 年）。与此同时，借鉴近代历史，越来越多的实证研究证实，在过去几十年中，农业增长在减少贫困方面比农业以外的增长更有效。 ${}^1$${}^1$^(1){ }^{1}

Yet, the continuing relevance of these findings to support a dominant role for agricultural growth in poverty reduction going forward was also questioned. Growth had been strong in many developing countries, and the share of agriculture in these economies had declined. Economies had become more open, following globalization, making food more tradable and reducing the relevance of insights from closed economy models. And the dismal performance of African agriculture during much of the 1990s and 2000s, did not inspire much hope for reliance on that sector to drive
然而，这些发现对于支持农业增长在未来减贫中发挥主导作用的持续相关性也受到质疑。许多发展中国家的增长势头强劲，而农业在这些经济体中的份额有所下降。随着全球化的发展，经济变得更加开放，使食品更具贸易性，并降低了封闭经济模型的见解的相关性。在 1990 年代和 2000 年代的大部分时间里，非洲农业的惨淡表现并没有激发人们对依赖该部门来推动的希望

a growth and poverty reduction agenda. In this view, productivity in agriculture, and especially in African smallholder agriculture, is so low compared with the other sectors and food sufficiently tradeable, that poverty reduction is much more likely to come from urbanization, i.e. facilitation of migration out of agriculture, and industrialization, greater reliance on food trade, and a radical transformation of the agricultural sector (into highly mechanized largescale farming) (Collier and Dercon, 2014; Dercon and Gollin, 2014).
增长和减贫议程。根据这种观点，农业的生产率，特别是非洲小农农业的生产率，与其他部门相比是如此之低，而且粮食是可充分贸易的，因此减贫更有可能来自城市化，即促进农业和工业化的迁移，对食品贸易的更大依赖，以及农业部门的根本转型（向高度机械化的大规模农业）（Collier和Dercon， 2014;Dercon 和 Gollin，2014 年）。

Against this background, the participants in a workshop on “Agriculture, structural transformation and poverty reduction”, organized at the World Bank in late 2013, set out to update and fine-tune the empirical evidence on the relationship between sectoral growth and poverty reduction. They further zoomed in on the structural factors and policy environments conditioning the conversion of growth in the different sectors into poverty reduction, with special attention to the role of the structural (and spatial) transformation, i.e. the labor reallocation from (rural) agriculture to (urban) nonagriculture.
在此背景下，2013年底在世界银行举办的“农业、结构转型和减贫”研讨会的与会者着手更新和调整关于部门增长与减贫之间关系的经验证据。他们进一步放大了制约不同部门增长转化为减贫的结构性因素和政策环境，特别关注结构性（和空间）转型的作用，即劳动力从（农村）农业到（城市）非农业的重新分配。

Much of the more recent literature on the topic has been econometric, mostly focused on comparing the differences in aggregate poverty effects from growth across the sectors. Given limited sample sizes, it often paid only limited attention to potential heterogeneity in the effects, across agricultural and nonagricultural subsectors, across countries at different levels of development, or even across different poverty outcomes, such as nutrition. Given the econometric focus, it also rarely distinguished between growth resulting from increases in productivity and growth from other sources, such as price changes, and relatedly the possibly substantially different impacts of productivity growth in open and closed
关于该主题的许多最新文献都是计量经济学的，主要集中在比较各部门增长对总体贫困影响的差异。由于样本量有限，它通常只关注农业和非农业子部门之间、不同发展水平的国家，甚至不同贫困结果（如营养）之间影响的潜在异质性。鉴于计量经济学的关注点，它也很少区分生产率提高带来的增长和来自其他来源（如价格变化）的增长，以及相关的公开和封闭生产率增长可能截然不同的影响

Fig. 1. Relationship between per capita GDP and poverty change from a productivity increase equal to $1\mathrm{\%}$$1\mathrm{\%}$1%1 \% of GDP (single country simulations). Source: Ivanic and Martin, 2018 .
图 1.人均 GDP 与贫困之间的关系从等于 GDP 的生产率增长 $1\mathrm{\%}$$1\mathrm{\%}$1%1 \% 变化（单一国家模拟）。资料来源：Ivanic 和 Martin，2018 年。
economies, an important insight highlighted by Matsuyama (1992). The literature further abstracted often from the role of the sectoral interactions (between agriculture and nonagriculture) and their drivers, the effectiveness of different interventions in getting agricultural or nonagricultural growth going, including through structural transformation, and last, but not least, the eventual impact of different financing modalities for poverty.
经济，Matsuyama （1992） 强调了一个重要的见解。文献通常进一步从部门互动的作用（农业和非农业之间）及其驱动因素、不同干预措施在促进农业或非农业增长方面的有效性（包括通过结构转型）以及最后但并非最不重要的一点是，不同融资方式对贫困的最终影响。

The eight papers in this special issue, retained after a standard refereeing process coordinated by us under the auspices of the World Development Editor in Chief, begin to address these gaps. Three papers are global/cross-country in scope (Ligon and Sadoulet; Ivanic and Martin; Eberhardt and Vollrath), while the others take a more region-specific lens; four of them focused on Africa (Dorosh and Thurlow; Kirk, Kilic and Carletto; Diao and McMillan; Adam, Bevan and Gollin), and one on a recent successful poverty reducer from South Asia, Bangladesh (Emran and Shilpi). The papers are essentially empirical and policy oriented in spirit. They pay great attention to the magnitudes of the different effects and their sensitivity to different assumptions and are strongly motivated by theory. They are also pluralistic in their analytical approaches, using both econometric estimation techniques and calibrated computable general equilibrium (CGE) model simulations linked with household models to explore the issues. The following are eight broad insights that emerged.
本期特刊中的八篇论文，在世界发展主编的主持下，经过标准的审稿程序后保留下来，开始解决这些差距。三篇论文是全球/跨国范围的（Ligon 和 Sadoulet;伊万尼克和马丁;Eberhardt 和 Vollrath），而其他人则采取了更特定于地区的视角;其中 4 个侧重于非洲（Dorosh 和 Thurlow;Kirk、Kilic 和 Carletto;Diao 和 McMillan;Adam、Bevan 和 Gollin），以及一篇关于南亚孟加拉国最近成功的减贫者（Emran 和 Shilpi）的论文。这些论文本质上是实证的，在精神上是以政策为导向的。他们非常关注不同影响的大小及其对不同假设的敏感性，并受到理论的强烈激励。他们的分析方法也是多元化的，使用计量经济学估计技术和与家庭模型相关的校准可计算一般均衡 （CGE） 模型模拟来探索这些问题。以下是出现的八大见解。

First, the proposition that growth in agriculture is in general (two to three times) more effective at reducing poverty than an equivalent amount of growth generated outside agriculture remains confirmed. This holds irrespective of the empirical method used (econometric, controlling for the endogeneity of growth, as in Ligon and Sadoulet, or CGE model simulations as in Ivanic and Martin or Dorosh and Thurlow). The finding also does not change when considering the distribution of welfare measures within countries or across countries (Ligon and Sadoulet) ${}^2$${}^2$^(2){ }^{2} or when using poverty
首先，农业增长在减少贫困方面通常比同等数量的农业以外增长更有效（两到三倍）这一命题仍然得到证实。无论使用何种实证方法（计量经济学，控制生长的内生性，如 Ligon 和 Sadoulet，或 CGE 模型模拟，如 Ivanic 和 Martin 或 Dorosh 和 Thurlow），这都成立。在考虑福利措施在国家内部或国家之间的分配（Ligon 和 Sadoulet） ${}^2$${}^2$^(2){ }^{2} 或利用贫困时，这一发现也没有改变

to growth semi-elasticities instead of elasticities (Dorosh and Thurlow). ${}^3$${}^3$^(3){ }^{3} This result holds more strongly when the experiment considered is, as in Ravallion and Datt (1996), an increase in GDP of equal size across sectors than an equal increase in GDP growth in each sector, but in poorer economies-where agriculture is a larger share of GDP-it holds for both experiments.
增长半弹性而不是弹性（Dorosh 和 Thurlow）。 ${}^3$${}^3$^(3){ }^{3} 当所考虑的实验是，如 Ravallion 和 Datt （1996） 所考虑的实验时，这一结果更为成立，即各部门相同规模的 GDP 增长比每个部门 GDP 增长相同，但在较贫穷的经济体中——农业在 GDP 中所占的份额更大——它适用于这两个实验。

Second, the advantage of agriculture over nonagriculture in reducing poverty is largest for the poorest in society (Ligon and Sadoulet) and ultimately disappears as countries become richer. This is again borne out both by the econometric (Ligon and Sadoulet) and CGE model simulation results (Ivanic and Martin) (Fig. 1). Similarly, Ligon and Sadoulet find stronger progressivity in the poverty reducing effect of agricultural growth over nonagricultural growth when literacy rates are lower, but could not discern any systematic effect of initial inequality.
其次，农业在减少贫困方面优于非农业的优势对社会中最贫困的人来说是最大的（Ligon 和 Sadoulet），并且最终会随着国家变得更富裕而消失。计量经济学（Ligon 和 Sadoulet）和 CGE 模型模拟结果（Ivanic 和 Martin）（图 1）再次证实了这一点。同样，Ligon 和 Sadoulet 发现，当识字率较低时，农业增长的减贫效果比非农业增长具有更强的渐进性，但无法辨别初始不平等的任何系统性影响。

These two sets of findings are overall consistent with the earlier cross-country findings reported in Christiaensen, Demery and Kuhl (2011) and underscore the continuing role agriculture could play in accelerating poverty reduction, especially in Africa, where the world’s poverty is increasingly concentrating, and South Asia, which also still houses one third of the world’s extreme poor (Castaneda et al., 2018).
这两组发现与 Christiaensen、Demery 和 Kuhl （2011） 中报告的早期跨国研究结果总体一致，并强调了农业在加速减贫方面可以发挥的持续作用，特别是在非洲，世界贫困日益集中，南亚仍然拥有世界上三分之一的极端贫困人口（Castaneda 等人， 2018).

Third, there is substantial heterogeneity in the povertyreducing effects of nonagriculture across its different subsectors (Dorosh and Thurlow), with poverty to growth elasticities for trade and transport services closer to those of agriculture and those for manufacturing, especially agro-processing, at times even exceeding them. The poverty-reducing effects of an equal amount of growth in mining, on the other hand, but also in finance, and business and government services are much more limited. These results are based on CGE model simulations, thereby accounting for the differential strength of the intersectoral linkages. Increasing the productivity of trade and transport reduces transaction costs for all marketed products for example, which is particularly beneficial for the agents in the sectors whose products have high margins, such as agriculture and food. Second, trade services are often also provided by low-paid informal traders, such that productivity growth in trade and transport services can have both direct and indirect linkages to the poor. Adam, Bevan and Gollin (also in this special issue) find similarly a substantial increase in the incomes of unskilled and rural workers in Tanzania from reducing transaction
第三，非农业在其不同子部门（Dorosh 和 Thurlow）的减贫效果存在很大异质性，贸易和运输服务的贫困到增长弹性更接近农业和制造业，尤其是农产品加工的弹性，有时甚至超过它们。另一方面，采矿业以及金融、商业和政府服务业等量增长的减贫效果要有限得多。这些结果基于 CGE 模型模拟，从而解释了部门间联系的差异强度。例如，提高贸易和运输的生产力可以降低所有上市产品的交易成本，这对农产品和高利润行业（如农业和食品）的代理商特别有利。其次，贸易服务通常也由低收入的非正规贸易商提供，因此贸易和运输服务的生产率增长可以与穷人产生直接和间接的联系。Adam、Bevan 和 Gollin（也在本期特刊中）同样发现，减少交易使坦桑尼亚非技术工人和农村工人的收入大幅增加

costs in transport, especially when the gains are obtained from a reduction in rents.
运输成本，尤其是当收益来自租金减免时。

Fourth, the advantages of growth in agriculture over growth in nonagriculture in reducing poverty can also extend to other welfare outcomes such as food insecurity and malnutrition, but tend to be more subject to the market context (depth of local food markets), the type of agricultural income growth (for commercial purposes or own consumption) and, when grown for own consumption, depending on the nutritional value of the crop. Recent cross-country evidence by Headey (2013) suggests for example that agricultural growth is also the most effective way to fight malnutrition, possibly because it is more effective at increasing the incomes of the poor, as shown above. Kirk, Kilic and Carletto in this issue further examine this proposition and highlight that not all agriculture will be equally good for reducing poverty or malnutrition. In their analysis from Uganda, focused on nutrition, children’s long run nutritional status correlates negatively with the share of income from crop production, especially among the older and poorer subset of children. This follows from the large share of low-protein staple production for own consumption among the households in this subsample (such as cassava and plantain). While they find the effect to be small, the findings underscore the importance of context and the need for further disaggregation within agriculture and non-agriculture, especially when deciding to promote certain sectors to improve nutritional outcomes.
第四，在减少贫困方面，农业增长相对于非农业增长的优势也可以延伸到其他福利结果，如粮食不安全和营养不良，但往往更多地受市场环境（当地食品市场的深度）、农业收入增长类型（用于商业目的或自用）以及当种植供自用时， 取决于作物的营养价值。例如，Headey （2013） 最近的跨国证据表明，农业增长也是对抗营养不良的最有效方式，这可能是因为它更有效地增加穷人的收入，如上所示。Kirk、Kilic 和 Carletto 在本期中进一步研究了这一命题，并强调并非所有农业在减少贫困或营养不良方面都同样有益。在他们来自乌干达的分析中，重点关注营养，儿童的长期营养状况与农作物生产收入份额呈负相关，尤其是在年龄较大和较贫穷的儿童群体中。这是因为该子样本中家庭自用的低蛋白主食生产（如木薯和车前草）所占的份额很大。虽然他们发现影响很小，但研究结果强调了环境的重要性以及在农业和非农业内部进一步分类的必要性，尤其是在决定促进某些部门以改善营养结果时。

Fifth, the degree of tradability of food (and nonfood) and the range of economies experiencing the increase in productivity are important considerations in determining the advantage of agriculture over non-agriculture in reducing poverty, though CGE simulations for 315,000 households from 31 countries indicate that agriculture’s advantage holds empirically, both under open (food is tradable) and closed (food is non-tradable) economy assumptions and when productivity growth is confined to one country or widespread (across all developing or all countries) (Ivanic and Martin). However, the source of the poverty reducing benefits from agricultural productivity growth changes as innovations are more widely adopted, moving from increases in producer returns (and wage labor opportunities) to reductions in consumer prices. The robustness of the gain across degrees of openness raises questions about the conclusion in Dercon (2009) that agricultural growth is a priority for poverty reduction only in landlocked African economies.
第五，食品（和非食品）的可贸易程度和生产率提高的经济体范围是确定农业在减贫方面优于非农业的优势的重要考虑因素，尽管对来自 31 个国家的 315,000 个家庭的 CGE 模拟表明，农业的优势在经验上是成立的，无论是在开放（粮食是可贸易的）和封闭的（粮食是不可贸易的）经济假设下，还是在生产率增长仅限于一个的情况下国家或广泛（在所有发展中国家或所有国家）（Ivanic 和 Martin）。然而，随着创新得到更广泛的采用，从生产者回报（和雇佣劳动机会）的增加转变为消费者价格的降低，农业生产力增长带来的减贫效益的来源发生了变化。跨开放程度的收益的稳健性引发了对 Dercon （2009） 的结论的质疑，即农业增长仅在非洲内陆经济体是减贫的优先事项。

Sixth, rising agricultural productivity not only reduces poverty by releasing (agricultural) labor to nonagricultural activities, it can also do so by pulling surplus labor from less productive home production into agriculture (Emran and Shilpi). When agricultural productivity increases, poor households may gain directly as producers, when costs fall more than prices or indirectly, as consumers through lower prices, or as agricultural laborers through increased employment and higher wages. The latter channel is especially important in densely populated countries with welldeveloped agricultural wage labor markets as in Asia. ${}^4$${}^4$^(4){ }^{4} The poverty reducing potential via the labor market channels depends on the nature of the technology (labor (or land) saving), inducing either an inward (or outward) shift of the agricultural labor demand curve, and thus a decline (increase) in agricultural wages and employment. Emran and Shilpi, further show that the agricultural wage and employment effects do not have to be symmetrical however, and
第六，农业生产率的提高不仅通过将（农业）劳动力释放给非农业活动来减少贫困，还可以通过将生产率较低的家庭生产中的剩余劳动力拉到农业中来实现这一目标（Emran 和 Shilpi）。当农业生产率提高时，贫困家庭可能作为生产者直接受益，当成本下降幅度超过价格时，或者通过降低价格间接地作为消费者受益，或者通过增加就业和提高工资作为农业劳动者。后一个渠道在亚洲等农业工资劳动力市场发达的人口稠密国家尤为重要。 ${}^4$${}^4$^(4){ }^{4} 通过劳动力市场渠道实现的减贫潜力取决于技术的性质（节省劳动力（或土地）），导致农业劳动力需求曲线向内（或向外）移动，从而导致农业工资和就业的下降（增加）。Emran 和 Shilpi 进一步表明，农业工资和就业效应不一定是对称的，并且

that little or no increase in agricultural wages and a decline in agricultural wage employment may be consistent with poverty reduction, since a substantial increase in household labor supply to a more productive agricultural activity (away from less productive home production) can lead to a significant reduction in poverty, even with little increase in wages. This holds especially when lowproductivity home production is prevalent, as they observe in Bangladesh. ${}^5$${}^5$^(5){ }^{5} Overall, the case study findings confirm the positive effect of rising agricultural productivity (here instrumented through rainfall shocks) on poverty reduction. They further highlight the continuing importance of putting “surplus” labor in the form of underemployed and unemployed family labor, to more productive use and that this can be done both by reallocating it to nonagriculture (as discussed in the next point), but also to agriculture.
农业工资很少或没有增加和农业工资就业下降可能与减贫是一致的，因为大幅增加家庭劳动力供应以从事生产率更高的农业活动（远离生产率较低的家庭生产）可以显著减少贫困，即使工资几乎没有增加。当低生产率的家庭生产普遍存在时，情况尤其如此，正如他们在孟加拉国所观察到的那样。 ${}^5$${}^5$^(5){ }^{5} 总体而言，案例研究结果证实了农业生产力的提高（这里通过降雨冲击来衡量）对减贫的积极影响。他们进一步强调了将“剩余”劳动力（以就业不足和失业的家庭劳动力的形式）用于更有成效的利用的持续重要性，这既可以通过将其重新分配给非农业（如下一点所讨论）来实现，也可以通过将其重新分配给农业来实现。

Seventh, reallocation of labor from agriculture, where most of the poor are currently located, to nonagriculture, which often is more skill intensive and where labor productivity tends to be higher, is an important channel through which poverty can be reduced. In many low-income countries (including in Africa) where food is primarily locally produced and consumed, increasing productivity growth in agriculture is often a precondition for releasing agricultural labor without creating hunger and starvation (Diao and McMillan). Yet, several structural factors further condition the speed and poverty reducing effects from such a reallocation of labor (including productivity growth outside agriculture) (Diao and McMillan). Eberhardt and Vollrath emphasize the importance of the elasticity of agricultural output with respect to labor in affecting the speed of structural transformation (and thus the potential contribution of labor reallocation to poverty reduction). In particular, they show that for an equivalent increase in agricultural total factor productivity (TFP), holding total agricultural output constant, economies with a low elasticity will be able to release a much larger amount of labor from agriculture to work in nonagriculture, than economies with a large elasticity. As a result, low elasticity economies will be able to develop faster than highelasticities ones. ${}^6$${}^6$^(6){ }^{6} Employing panel data from 128 countries, they further show temperate and/or cold climate regions to have low, and tropical and highland regions to have much higher, agricultural output to labor elasticities. This provides an additional reason why structural change and development may have lagged in the latter. It further suggests that even larger increases in agricultural productivity will be needed to achieve the same effects as in temperate regions, or that progress will simply be slower.
第七，将劳动力从目前大多数贫困人口所在的农业重新分配给非农业，非农业往往是技能密集度更高、劳动生产率往往更高的非农业，这是减少贫困的重要渠道。在许多粮食主要由当地生产和消费的低收入国家（包括非洲），提高农业生产率通常是释放农业劳动力而不造成饥饿的前提条件（Diao 和 McMillan）。然而，几个结构性因素进一步制约了这种劳动力重新分配（包括农业以外的生产率增长）的速度和减贫效果（Diao 和 McMillan）。Eberhardt 和 Vollrath 强调了农业产出相对于劳动力的弹性在影响结构转型速度（以及劳动力重新配置对减贫的潜在贡献）方面的重要性。特别是，在农业总产出不变的情况下，如果农业全要素生产率（TFP）同等提高，与弹性大的经济体相比，低弹性经济体能够将更多的劳动力从农业中释放出来，用于非农业工作。因此，低弹性经济体将能够比高弹性经济体发展得更快。 ${}^6$${}^6$^(6){ }^{6} 他们使用来自 128 个国家的面板数据，进一步显示温带和/或寒冷气候地区的农业产出与劳动力的弹性要低得多，而热带和高原地区的农业产出与劳动力的弹性要高得多。这为后者的结构性变化和发展可能滞后提供了另一个原因。 它进一步表明，需要更大幅度的农业生产力提高才能达到与温带地区相同的效果，否则进展会更慢。

Adam, Bevan and Gollin further emphasize that the benefits of public investment may at times be felt more in sectors other than those that are the primary target of the interventions. Differentiating the urban space in Tanzania between the capital, Dar, and secondary cities/towns, they find for example that increased public investment in urban areas in Tanzania, particularly in its secondary cities, would lead to larger welfare benefits for rural and unskilled (i.e. poor) households than agricultural biased investments of a similar size. When the productivity benefits of public investment occur in non-agricultural sectors, relative food prices fall by less and the incentives for out-migration are moderated. Put differently, it is the fall in food prices and the increase in labor supply in the urban locations that transfer the gains from agriculturalbiased investments to urban households. They further show that because of the importance of the intersectoral labor and product
Adam、Bevan 和 Gollin 进一步强调，公共投资的好处有时可能在干预主要目标以外的部门更能感受到。他们区分了坦桑尼亚首都、达尔和二级城市/城镇的城市空间，例如，他们发现，与类似规模的偏农业投资相比，增加坦桑尼亚城市地区，特别是二级城市的公共投资将为农村和非技能（即贫困）家庭带来更大的福利。当公共投资的生产率效益发生在非农业部门时，相对食品价格的下降幅度就会减少，向外迁移的激励也会减弱。换句话说，正是食品价格的下跌和城市地区劳动力供应的增加，将偏向农业的投资的收益转移到了城市家庭。他们进一步表明，由于跨部门劳动和产品的重要性