学术前沿 | 国际顶级农经期刊AJAE2020年10月第5期文章摘要及翻译（下）

Original 启研学社三农大数据 2022-12-31

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启研学社由知名学者担任学术顾问，高校师生与企研数据科学团队联合组建，以大数据资源及相关技术助力中国学术与智库研究为宗旨的研究组织。团队当前的主要目标是挖掘经济社会大数据资源在学术和智库领域的应用价值，开展学术大数据治理研究，以及探索大数据分析技术融入中国经济社会研究的可行进路。

昨天，启研学社的小伙伴为大家带来了国际顶级农经期刊 American Journal of Agricultural Economics 2020年10月第5期文章摘要及翻译中的6篇（点此回顾），今天，为大家介绍余下的7篇。

技术进步增加了农业产量风险吗？来自农作物保险生物科技认证机构的证据

玉米苗种培育和基因改良的技术进步会降低产量风险的传统观念受到了最近一些研究的挑战，即事实可能相反。大量的实证研究表明，上世纪90年代到本世纪各种转基因作物（包括玉米）的产量对气候变得越来越敏感。在上述观点的基础上，本文通过构建气候变化模型发现性状育种和遗传改良技术的进步事实上增加了农业风险，同时我们要注意气候变化对未来农业产出稳定性的影响。我们使用玉米产量和美国联邦作物保险计划的数据来验证上述发现的正确性。首先，分析1988和2012这两年（干旱年份）的玉米产量状况，我们发现尽管这两年的干旱情况非常相似，但2012年的产量更高。其次，从2008至2011年联邦农作物保险计划生物技术认证机构（BE）的并行数据看，我们发现以每单位保险的赔付率来衡量，根据BE投保的农作物的风险要低得多（BE为转基因杂交品种的种植者提供了大量的保险优惠，反映出政策制定者认为杂交品种的产量风险较低）。我们还发现，当气候环境不太有利时，产量风险的差异会增加。

Goodwin, B. K. and N. E. Piggott (2020). "Has Technology Increased Agricultural Yield Risk? Evidence from the Crop Insurance Biotech Endorsement." American Journal of Agricultural Economics 102(5): 1578-1597.

The conventional wisdom that technological advances in seed breeding and genetic modification of corn traits have lowered yield risk has recently been challenged by research that argues that the converse is true. The implications of this research have been applied to models of climate change and have led to the conclusion that these advances have actually increased agronomic risk, such that climate change is asserted to raise important concerns regarding the stability and viability of agricultural output in the future. In a large body of empirical work, the argument is based upon assertions that corn yields have become more sensitive to weather stresses. This increased sensitivity has coincided with the introduction of a variety of genetically engineered (GE) crops in the 1990s and 2000s. We use corn yields and data from the US federal crop insurance program to evaluate these claims. An initial examination of yield responses to droughts in 1988 and 2012 suggests more robust yields in the latter period, in spite of very comparable weather stresses. We next consider side‐by‐side data collected under the Biotech Endorsement (BE) to the federal crop insurance program between 2008 and 2011. This endorsement provided substantial discounts for growers using certain GE hybrids, reflecting policymakers' beliefs that these hybrids had lower yield risk. We find that risk, as measured by the rate of indemnities paid per units insured, was significantly lower for crops insured under the BE. We also find that the difference in risk tends to be greater when growing conditions are less favorable.

埃塞俄比亚的耕地细碎化和粮食不安全问题

本文从耕地细碎化造成的经济后果出发，重点研究耕地细碎化对粮食不安全的影响。在现有文献的基础上，本文考虑到了耕地破碎的外生性、度量方法及其对各种福利指标的影响。本文运用生活水平测量调查数据（该数据非常适合于解决这些问题），发现土地细碎化降低了埃塞俄比亚的粮食不安全问题。这一结果对如何衡量细碎化以及如何解决外生性问题都是有用的。此外，本文还发现，耕地破碎化增加了不同家庭种植作物的种类，缓解了低雨量对粮食安全的不利影响。

Knippenberg, E., et al. (2020). "Land Fragmentation and Food Insecurity in Ethiopia." American Journal of Agricultural Economics 102(5): 1557-1577.

This paper builds on the literature surrounding the economic consequences of land fragmentation, focusing on the effects of such fragmentation on food insecurity rather than agricultural productivity. Building on existing literature, it accounts for concerns regarding the exogeneity of fragmentation, its measurement, and the importance of considering impacts in terms of different welfare metrics. Using data from the Living Standards and Measurement Survey (LSMS) that are well‐suited to addressing these issues, the analysis finds that land fragmentation reduces food insecurity in Ethiopia. This result is robust to how fragmentation is measured and to how exogeneity concerns are addressed. Further, the paper finds that land fragmentation mitigates the adverse effects of low rainfall on food security. This is because households with diverse parcel characteristics can grow a greater variety of crop types.

第二次拍卖价格中的认知能力与投标行为：一项实验研究

本文考察了在第二次价格拍卖中，认知能力与竞价策略之间存在何种联系（如果有的话）。尽管如实披露是一种弱占优势的策略，但之前的实验一直观察到超额竞价，这使得利用这种拍卖推断本土价值存在问题。研究认知能力的影响是很重要的，因为它有助于判断当前的出价是否符合拍卖品内在价值。研究结果表明，认知能力较强的受试者的行为更符合理论，认知能力部分解释了竞价行为的异质性。我们的结果表明，在本土估值研究中考虑受试者的认知能力有助于识别真正的潜在需求状况。

Lee, J. Y., et al. (2020). "Cognitive Ability and Bidding Behavior in Second Price Auctions: An Experimental Study." American Journal of Agricultural Economics 102(5): 1494-1510.

This paper examines what connection, if any, there is between cognitive ability and bidding strategy in second price auctions. Despite truthful revelations being a weakly dominant strategy, previous experiments have consistently observed overbidding, which makes the use of such auctions for inferring homegrown values problematic. Examining the effect of cognitive ability is important, as it may help identify when one can reliably recover values from observed bids. The results indicate that more cognitively able subjects behave in closer accordance with theory, and that cognitive ability partially explains heterogeneity in bidding behavior. Our results suggest that considering subjects' cognitive ability in homegrown valuation studies can help identify the true underlying demand conditions.

正规信贷准入与新技术采纳：来自印度的证据

本文考察了信贷准入的改善是否会影响新技术的采用。本文运用印度农村额外收入调查数据、农村经济与人口调查的家庭面板数据，以及印度储备银行的银行分行数据，评估了银行分行扩张对印度家庭使用高产量品种种子的影响。本文使用印度政府曾实施的社会银行政策作为地区银行准入的外生变量，这一政策在1977年至1990年期间生效，它推动银行在金融欠发达地区开设了更多的分支机构。研究发现，在社会银行时期（1977-1990年），初始金融发展水平较低的地区新开分行数量显著增加。此外，在该时期，经济欠发达地区的家庭更有可能采用高产量品种种子，这与假设相一致，即信贷准入的改善是采用新技术的一个重要因素。最后，本文使用地理覆盖面更广的区域面板数据进行补充分析，得到如下结论：正规信贷可获得性对高产量品种种子的使用同样具有积极影响，并且没有发现在经济较发达地区和经济欠发达地区之间，高产量品种种子使用在历史上存在的差异。

Mukherjee, S. (2020). "Access to Formal Banks and New Technology Adoption: Evidence from India." American Journal of Agricultural Economics 102(5): 1532-1556.

This article examines whether improvement in access to credit affects new technology adoption. Using the Additional Rural Incomes Survey and Rural Economic and Demographic Survey Indian household panel data, and bank branch data from the Reserve Bank of India, I evaluate the impact of bank branch expansion on high‐yielding variety seed adoption by Indian households. I use the Indian government's social banking policy to provide exogenous variation in district bank access. This policy, in effect between 1977 and 1990, forced banks to open more branches in financially less developed areas. I find that districts with lower initial financial development experienced a significant rise in new branch openings during the social banking period (1977–1990). Further, I find that households in financially less developed districts were more likely to adopt high‐yielding variety seeds during the social banking period, consistent with the hypothesis that access to credit is an important determinant of new technology adoption. A supplemental analysis using district panel data, which has broader geographic coverage, yields the same positive impact of formal credit access on high‐yielding variety seed usage and provides no evidence of historical trend differences in the use of high‐yielding variety seeds between more and less financially developed areas.

地下知识：通过实验拍卖估算土壤信息传递的影响

土壤退化是许多发展中国家面临的一个严重的环境问题。发展中国家通常需要使用化肥来提高作物产量，但是小农户通常没有足够的关于其土壤养分水平的信息，无法对化肥的使用做出利润最大化决策。我们进行了两轮实验拍卖，用来确定向肯尼亚西部的农民提供廉价土壤检测试剂盒的信息和肥料建议是否会影响他们的行为和优化投入选择的能力。我们拍卖了有机和无机农业投入品，将农户分层进行信息处理，并使用双重差分和三重差分估计对数据进行分析。我们发现，提供土壤信息对农民的投入支付意愿有显著影响。然后，我们使用蒙特卡洛模拟（Monte Carlo simulations）来展示个性化的土壤检测有可能给农民带来高额的净收益。这些结果表明，土壤测试可以成为提高本区域粮食安全的一种具有成本效益的方法。

Murphy, D. M. A., et al. (2020). "Underground Knowledge: Estimating the Impacts of Soil Information Transfers Through Experimental Auctions†." American Journal of Agricultural Economics 102(5): 1468-1493.

Soil degradation, a serious environmental problem in many developing countries, often necessitates the use of fertilizers to improve crop yields. However, smallholders usually do not have sufficient information about their soil nutrient levels to make profit‐maximizing decisions about fertilizer usage. We conducted two‐round experimental auctions to determine whether providing information and fertilizer recommendations from inexpensive soil testing kits to farmers in western Kenya affected their behavior and ability to optimize their input choices. We auctioned organic and inorganic agricultural inputs, dividing farmers into information treatments, and analyzed the data using double and triple difference estimations. We find that providing soil information has significant effects on farmers' willingness to pay for inputs. We then use Monte Carlo simulations to show that there is potential for high net benefits to farmers from individualized soil tests. These results suggest that soil testing can be a cost‐effective method to increase food security in the region.

水权退出计划的目标：来自堪萨斯州的证据

本文评估了堪萨斯州阿肯色河上游流域保护区储备增强计划的用水影响，该计划是一项旨在减少高原含水层（Aquifer）耗竭的水权退出计划。首先，我使用固定效应模型，通过农民的匹配样本来确定项目对退耕者的用水量的影响。我发现，在项目中退出的被用来灌溉的每一英亩代表了每年本应使用的1.28英亩英尺水(即原先灌溉的土地，现在参与这个项目后无用水权了。而1英亩地约1.28英尺深的年用水量)。此外，并未发现农民为了满足项目资格（eligibility）要求而增加用水量。其次，我用probit回归进行估计，以确定哪些因素对农民退出水权（退耕）的可能性影响最大。根据概率回归的结果，我模拟了政策区域外的登记决策，以评估项目的特点如何影响其成本效益，以及如何改进政策设计。我发现，以过去的取水水平为基础的激励措施，每支付一美元就能减少更多的用水量。

Rosenberg, A. B. (2020). "Targeting of Water Rights Retirement Programs: Evidence from Kansas." American Journal of Agricultural Economics 102(5): 1425-1447.

This article assesses the water use impacts of the Conservation Reserve Enhancement Program in the Upper Arkansas River basin in Kansas, a water rights retirement program aimed at reducing depletion of the High Plains Aquifer. First, I use a fixed effects model with matched samples of farmers to determine the effect of the program on the water use of individuals who retire acreage. I find that every acre authorized for irrigation that is retired in the program represents about 1.28 acre‐feet of water that would have been used each year. Further, I do not find evidence that farmers increase their water use in an effort to satisfy program eligibility requirements. Second, I estimate a probit regression to determine which factors most influence the probability that a farmer retires a water right. Using the results of the probit regression, I then simulate enrollment decisions outside of the policy region to assess how features of the program impact its cost effectiveness and how the policy design could be improved. I find that programs that base incentives on past levels of water extraction lead to more water use reductions per dollar paid.

市场结构和乙醇（Ethanol）扩张对土地分配的局部影响：空间显式分析

我们研究了当地玉米采购（procurement）市场的结构如何塑造（shape）乙醇产能扩张对周边地区玉米种植决策的影响。我们首先将竞争强度刻画为工厂产能空间结构的函数，然后从经济上估计在网格单元水平上（at the grid‐cell level），玉米种植面积对竞争强度的响应。我们利用已估计的参数进行事实和反事实实验，量化不同的产能扩张来源对竞争强度的影响，并最终量化其对土地覆盖的空间模式的影响。我们发现，给定规模的乙醇产能扩张会对玉米的总土地转化率产生不同的影响，这一影响取决于乙醇产能扩张的来源（即新工厂的进入、现有（incumbent）工厂的扩张或者扩张发生的地点）。且竞争强度增加最多的扩张也会引发最多的土地转化。这是因为，随着玉米空间竞争的加剧，工厂只能从集聚生产区域采购更多的玉米，而这些额外的玉米只能通过土地转换得到。我们还发现，竞争溢出效应会引发不在新工厂或产能扩大的工厂采购区域内的网格单元的土地转换。我们的结果强调了，在量化与乙醇产能扩张相关的地方土地利用变化时，考虑市场结构的重要性。

Wang, Y., et al. (2020). "Market Structure and the Local Effects of Ethanol Expansion on Land Allocation: A Spatially Explicit Analysis." American Journal of Agricultural Economics 102(5): 1598-1622.

We investigate how the structures of local corn procurement markets shape the effect of expansion in ethanol production on corn planting decisions in surrounding areas. We first characterize competition intensity as a function of the spatial structure of plant capacities and then econometrically estimate the response in corn acreage to competition intensity at the grid‐cell level. We use the estimated parameters to conduct factual and counterfactual experiments quantifying the effect of different sources of capacity expansion on competition intensity and, ultimately, spatial patterns of land cover. We find that an expansion of ethanol capacity of a given magnitude can have disparate effects on total land conversion to corn depending on its source, that is, whether it is due to plant entry, expansion of an incumbent plant, or the location where the expansion occurs. Expansions that increase competition intensity the most also trigger the most land conversion. This is because, as spatial competition for corn intensifies, plants are forced to procure more from the intensive margin, where additional corn can only be obtained from land conversion. We also find that competitive spillovers trigger land conversion in grid cells that are not within the procurement area of a new plant or of a plant that expands capacity. Our results underscore the importance of considering market structure when quantifying local land use changes associated with ethanol capacity expansion.

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