学术前沿丨农业经济学学科介绍及国内外前沿问题
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。
本人去年报考了浙江大学农业经济管理专业的硕士研究生，近期在导师的推荐下阅读了厦门大学邹至庄经济研究中心、经济学院陈煌老师的文章——《农业经济学学科介绍和国内外前沿问题》，在仔细研读后我写下这篇推文，以供读者学习交流。
一、农业经济学学科介绍
农业经济学最早用于分析农业生产者如何优化资源配置以达到生产效率最大化的目的。随后，著名农经学家、诺贝尔经济学奖获得者舒尔茨在研究中大量应用逐渐成熟的现代计量经济学方法，农业经济学逐渐成为一门以应用微观研究为主，关注农业生产、食品消费、减贫问题、环境资源与生产协调发展的综合性学科。农业经济学主要有如下领域和具体方向：
二、农业经济学发展趋势与国际前沿
上文提到农业经济学主要有如下三个方向：传统农业经济学、农业发展经济学与农业资源与环境经济学，而当前这三个研究方向的变化趋势可以概括为如下三个方面：一是传统农业经济学轻度缩水；二是农业发展经济学稳步成长；三是农业环境和资源经济学，其研究热度升温较快。
目前农业经济学国际前沿问题研究主要有以下几个方面（包括但不仅限于这些）∶
（1）农业生产力跨国之间的差异原因探究（Adamopoulos and Restuccia, 2014; Gollin et. al., 2014）；
（2）发达国家中农业生产者的风险管理策略研究，包括贷款、保险和差异化种植行为等（Singerman and Useche，2019；Vigani and Kathage，2019）；
（3）发展中国家推广农业保险的理论和实证检验，包括指标保险中基差风险的控制、投保需求的激励以及保险效果的评估（Cai et. al.，2015；Janzen and Carter, 2019）;
（4）发展中国家推广信贷服务的理论和实证检验，包括对信息不对称问题的解决等 （Hossain, et. al., 2019）；
（5）政府转移支付政策对农业生产、农户收入和生活以及农产品进出口的影响（Asher and Novosad，2020；Dustan，2020）；
（6）土地政策改革的效果评估，尤其关注产权、农场面积和土地生产力的关系（Muyanga, et. al., 2019；Bevis and Barrett, 2020）；
（7）技术采用的决定因素、成本效益分析，以及高附加值农业产业的发展（Chen，2020；Porteous, 2020）；
（8）在发达与欠发达国家中农村基础设施、农产品市场的可得性与弱势群体（儿童、妇女、老人）的营养健康的关系（Headey, et. al., 2019；Mo, et. al. 2020）；
（9）气候变化带来的农业生产风险识别，农村人口生活影响与适应性策略研究（Cui，2020）；
（10）环境约束与农业发展问题的矛盾与协调（发展中国家为主），例如化肥和农药的使用等（McArthur and McCord，2017）；
（11）各类环保政策效果的评估，包括政策成本和环保的等价经济收益评估（Brown, et. al., 2019）；
（12）水资源管理的政策创新、水市场发展和效果评估（Suárez, et. al., 2019）。
注：以上12篇文章摘要详见附录
三、农业经济学在中国的机遇、挑战与重要研究问题
目前农业经济学在中国面临的机遇可以归纳为如下三点：一是中央政府高度重视农业发展；二是我国面临农业发展的转型阶段，然而国外的模式不一定适合中国，因此我们急需一批农经学家因地制宜地研究出适合中国农业转型的政策建议；三是中国需要将农村发展的经验推广到与中国类似的发展中国家。
而中国的农经研究也面临着一些挑战：一是农业经济学依赖实证数据，但当前的数据库侧重于农户生活，对农业生产投入的收录不足，且使用起来不方便；二是国内早期多以定性方法分析农业经济学，目前因果推论问题并没有很好地解决，即研究方法缺乏科学性、严谨性。
当前国内农经重要的研究问题有如下几个方面（包括但不仅限于）：
（1）在保证粮食安全和农户收入的前提下，稳健扩大户均经营规模，逐渐释放农业劳动力，促进农业产业化、人口城镇化，最终达到走向现代化的目标（Sheng, et. al., 2019）；
（2）快速发展的信息与通讯技术在农业生产领域的应用，比如在农作物生长状况监控和化肥农药的使用方面的应用，农产品电子商务对农户收入、农业供应链以及消费者的影响；
（3）探索农业大数据的信息采集、数据应用以及计量方法；
（4）过去 40 年中国减贫成果经验总结，当前精准扶贫的成效评估以及进一步扶贫政策的制定，凝练出可供实证检验的经济学原理，讲好中国故事；
（5）评估政策性农业保险市场的成效以及探索农业银保联动的可能性，进一步探索改善农业信贷市场的可能性，以更为成熟稳健的农业金融服务体系支持经营规模扩展的大方向政策任务；
（6）探索以实证为依据，以乡村振兴为目标的具体乡村振兴实施策略；
（7）户口政策松绑的改革以及城市对进城务工家庭引导政策对农民工流动、城市定居的影响（Meng, 2012）；
（8）惠农政策、转移支付政策、基层管理政策对留守家庭的各方面经济生活改善的分析；
（9）农村教育资源普及和质量改进的措施探索，农村基层医疗水平的改善以及成效分析；
（10）完善缺水地区的灌溉管理制度，继续探索发展水交易市场；
（11）平衡畜牧业发展与农村污染防控的矛盾关系，平衡农业生产、农业加工行业发展与农村地区污染防治与管控（包括空气、水、土地等），有机农业发展的策略，政府各类生态补偿政策的成效评估。
四、总结
最后，作者针对目前存在的问题提出了一些建议，如增加农业经济学研究主题和研究方法的多样性、鼓励探索新领域，鼓励采用因果识别、RCT等前沿实证方法，鼓励使用大数据来分析政府的干预效果等等。
陈煌老师的这篇文章清楚地介绍了农业经济学的发展情况和前沿问题，特别是农业经济学在我国发展的情况。对于像笔者一样的“农经小白”来讲，这篇文章能够帮助我们初步地了解农业经济学，为今后进一步学习奠定基础。
关注我们！公众号对话框内发送关键词“20210201”获取陈煌老师《农业经济学学科介绍及国内外前沿问题》PDF版
五、附录
一、农业生产力跨国之间的差异原因研究
Abstract：Greenland and Glenn Farley for excellent research assistance. All potential errors are our own Economists have long recognized that cross-country differences in aggregate labor productivity are enormous. Recently, Caselli (2005) and Restuccia, Yang, and Zhu (2008), among others, have shown that these differences have a strong sectoral dimension. In particular, differences in agricultural labor productivity are far larger than those of the aggregate. Caselli (2005), for example, reports that the ratio of labor productivity in the ninetieth and tenth percentiles of countries is a factor of 22 in the aggregate, and a factor of 45 in agriculture. Because developing countries have most of their workers in agriculture, understanding why productivity differences in agriculture are so large is key to understanding world income inequality. There are a number of reasons one may be skeptical, however, about the agricultural productivity data underlying these conclusions. One may worry that agricultural output data may be badly measured, particularly in the world's poorest countries, where statistical agencies often have limited resources (Jerven 2013). The international prices used to aggregate agricultural goods to the country level may be better suited to richer countries than poorer countries, since international prices are quantity-weighted. More generally, skepticism may arise simply from the sheer magnitudes in agriculture, which dwarf the (already large) productivity differences in the aggregate. In this paper we re-examine the cross-country agricultural productivity data using new evidence from disaggregate sources. We focus on physical measures of labor productivity for the world's three staple grains—maize, rice, and wheat—which together account for roughly half of the calories consumed by the average individual. Because productivity in these crops is easy to measure, we avoid the "black-box" nature of output data from aggregate sources. Moreover, because crop yields are observed at many levels, from individual production units to national aggregates, we are able to cross-check macrolevel productivity statistics with micro-level estimates of productivity for these crops. We find that cross-country differences in the quantity of grain produced per worker are enormous, and at least as large as those of the agricultural sector as a whole. Moreover, we show that independent micro-level estimates of grain yields correspond very closely to their counterparts in aggregate data. We conclude that the large disparities in agricultural labor productivity are real, at least for staple grains, and are not merely an artifact of
mismeasurement or poor data quality
二、发达国家中农业生产者的风险管理策略研究
Ariel Singerman and Pilar Useche
University of Florida
Abstract: We elicit a measure of strategic uncertainty from growers by using an experimental game grounded on the theory of global games. This allows us to achieve the following: propose a mechanism for measuring strategic uncertainty aversion; compare growers' risk aversion to their strategic uncertainty aversion; explore how growers' strategic uncertainty aversion is affected by changes in group size and coordination requirement; and relate a strategic uncertainty aversion measure to growers' actual decisions to participate in an area-wide pest management program. In our experimental setting, we found that when the coordination requirement for a successful outcome is low, most growers see the strategic uncertainty posed by human interaction as more favorable in terms of expected payoffs relative to a game against nature. In contrast, when the coordination requirement is high, most growers expect lower payoffs and choose to coordinate less. We also found evidence that growers' strong beliefs about neighbors not coordinating negatively impacted their choices to coordinate. Our measure of strategic uncertainty was also found to influence the likelihood of growers to actually coordinate sprays. Our findings help explain why participation in area-wide pest management to control the vector of citrus greening across Florida has not been as widespread as expected; the strategic uncertainty involved in relying on neighbors has made many growers choose self-reliance in spraying despite the lower payoff.
Keywords: Area-wide pest management, citrus greening, global games, public goods, strategic uncertainty.
To risk or not to risk? Risk management and farm productivity
是否要冒风险？风险管理与农场生产率
Mauro Viganiᵃ and Jonas Kathageᵇ
ᵃ University of Gloucestershire.
ᵇ European Commission, Joint Research Centre (JRC), Seville, Spain
Abstract: Using survey data from French and Hungarian farms, we estimate the impacts of different risk management strategies and portfolios under varying levels of risk on total factor productivity. Results from a multinomial endogenous switching regression model show that the impacts can be positive or negative, depending on the risk management strategies adopted, the structure of the farming system, and the probability of risks. The choice of risk management strategies influences the farm's production costs and the allocation of resources. More complex risk management portfolios tend to have larger negative productivity impacts due to higher costs and the larger amount of resources subtracted from the production activity. Our results have important implications for risk management policies.
Keywords: Multinomial endogenous switching regression, risk management, risk probability, total factor productivity, wheat.
三、发展中国家推广农业保险的理论和实证检验
The effect of microinsurance on economic activities: Evidence from a randomized field experiment
小额保险对经济活动的影响：来自某一随机地区实验的证据
Hongbin Caiᵃ, Yuyu Chenᵇ, Hanming Fangᶜ, and Li-An Zhouᵈ
ᵃᵇᵈ Peking University
ᶜ University of Pennsylvania and NBER.
Abstract: We report results from a large, randomized field to study how access to formal microinsurance affects production and economic development. We induce exogenous variation in insurance coverage at the village level by randomly assigning performance incentives to the village animal husbandry worker who is responsible for signing farmers up for the insurance. We find that promoting greater adoption of insurance significantly increases farmers' sow production,and this effect seems to persist in the longer run; moreover, the increase in sow production in response to the sow insurance does not seem to be the result of the substitution of other livestock.
After the drought: The impact of microinsurance on consumption smoothing and asset protection
干旱之后：小额保险对消费平滑和资产保护的影响
Sarah A. Janzenᵃ and Michael R. Carterᵇ
ᵃ Kansas State University
ᵇ University of California
Abstract: To cope with shocks, poor households with inadequate access to financial markets can sell assets to smooth consumption and, or reduce consumption to protect assets. Both coping strategies can be economically costly and contribute to the transmission of poverty, yet limited evidence exists regarding the effectiveness of insurance to mitigate these costs in risk-prone developing economies. Utilizing data from an RCT in rural Kenya, this paper estimates that on average an innovative microinsurance scheme reduces both forms of costly coping. Threshold econometrics grounded in theory reveal a more complex pattern: (i) wealthier households primarily cope by selling assets, and insurance makes them 96 percentage points less likely to sell assets following a shock; (ii) poorer households cope primarily by cutting food consumption, and insurance reduces by 49 percentage points their reliance on this strategy.
Keywords: Insurance, consumption smoothing, asset smoothing, poverty, Kenya.
四、发展中国家推广信贷服务的理论和实证检验
Agricultural microcredit for tenant farmers: Evidence from a field experiment in Bangladesh
租户农民的农业小额信贷：来自孟加拉国某一地区实验的证据
Marup Hossainᵃ, Mohammadabdul Malekᵇ, Md. Amzad Hossainᶜ, Md. Hasib Rezaᵈ, And Md. Shakil Ahmedᵉ
ᵃ University of Florida
ᵇ Kyoto University & Research and Evaluation Division
ᶜ University of Virginia & Department of Economics, University of Dhaka
ᵈ East West University & Independent Research and Evaluation Cell (IERC), BRAC International
ᵉ Research and Evaluation Division, BRAC
Abstract: We study the impact of an agricultural microcredit program on the livelihoods of small, marginal, and landless tenant farmers in Bangladesh based on a Randomized Control Trial (RCT). Twenty percent of eligible households acquire at least one loan from the program within two years of the start of the intervention. Results show that access to credit has positive but imprecisely estimated effects on adoption of modern varieties (MV) of rice as well as rice yield. The microcredit program increases crop farm income but has no significant effect on total income or expenditure. Although the program does not have a significant effect on most economic outcomes, it demonstrates an increase in farm activities among the targeted farmers. Our study suggests that facilitating access to credit without addressing other constraints may not be enough to increase investment and profits of tenant farmers.
Keywords: Agricultural microcredit, field experiment, income diversification, machine learning model, tenant farmers.
五、政府转移支付政策对农业生产、农户收入和生活以及农产品进出口的影响
Rural roads and local economic development
乡村公路与当地经济发展
Sam Asherᵃ and Paul Novosadᵇ
ᵃ Johns Hopkins University
ᵇ Dartmouth College
Abstract: Nearly one billion people worldwide live in rural areas without access to national paved road networks. We estimate the impacts of India's $40 billion national rural road construction program using a fuzzy regression discontinuity design and comprehensive household and firm census microdata. Four years after road construction, the main effect of new feede roads is to facilitate the movement of workers out of agriculture. However, there are no major changes in agricultural outcomes, income, or assets. Employment in village firms expands only slightly. Even with better market connections, remote areas may continue to lack economic opportunities.
Can large, untargeted conditional cash transfers increase urban high school graduation rates? Evidence from Mexico City's Prepa S´ı
大量、无目标、有条件的现金转移能提高城市高中的毕业率吗？来自墨西哥城预科学校的证据
Andrew Dustan
Vanderbilt University
Abstract: This paper estimates the effects of a massive, minimally targeted conditional cash transfer program in Mexico City's public high schools on graduation rates, test scores, and school choice. Using a difference-in-differences approach that exploits variation in eligibility between students and cohorts within a high school, I find that this program had no appreciable effect on high school completion. The results are sufficiently precise to rule out policy-relevant effect sizes. Null effects persist for subgroups that could be candidates for a targeted program. End-of-high school exam scores are apparently unaffected by the program and effects on high school choices by eligible students are minimal. There is no evidence for heterogeneous effects with respect to implicit or explicit cost of attendance, suggesting that liquidity constraints are not a key driver of high school dropout in this urban setting. These results highlight the challenges of using cash to improve academic outcomes in cities.
六、土地政策改革的效果评估
Close to the edge: High productivity at plot peripheries and the inverse size-productivity relationship
接近边缘：土地边缘地带的高生产率以及规模与生产率的逆相关关系
Leah EM Bevisᵃ, Christopher B Barrettyᵇ
ᵃ Ohio State University
ᵇ Cornell University
Abstract: Smaller farms and plots appear more productive per hectare than larger ones in most developing country data. Using unique plot-level panel data from Uganda, with agricultural plots matched over a decade using geospatial location, we estimate the size-productivity relationship using variation in plot size over time under plot fixed effects, as well as variation in plot size within a farm, under household-period fixed effects. Like many other authors, we find that the observed inverse relationship arises at the plot, not farm, level, and that observable plot characteristics such as soil quality cannot explain the relationship. However, the plot perimeter/area ratio explains most of the inverse plot size-productivity relationship, reflecting an edge effect widely acknowledged in the agronomy literature wherein productivity is highest around the periphery of plots. We present suggestive evidence consistent with behavioral and biophysical mechanisms underpinning the edge effect.
Keywords: agriculture, behavioral, causal bounds, perceptions, edge effect, Uganda
Revisiting the farm size-productivity relationship based on a relatively wide range of farm sizes: Evidence from Kenya
基于相对较大的农场规模再研究农场的规模与生产率之间的关系：来自肯尼亚的证据
Milu Muyanga and T. S. Jayne
Michigan State University
Abstract: This paper revisits the inverse farm size-productivity relationship in Kenya. The study makes two contributions. First, the relationship is examined over a much wider range of farm sizes than most studies, which is particularly relevant in Africa given the recent rise o medium- and large-scale farms. Second, we test the inverse relationship hypothesis using three different measures of productivity including profits per hectare and total factor productivity, which are arguably more meaningful than standard measures of productivity such as yield or gross output per hectare. We find a U-shaped relationship between farm size and all three measures of farm productivity. The inverse relationship hypothesis holds on farms between zero and 3 hectares. The relationship between farm size and productivity is relatively flat between 3 and 5 hectares. A strong positive relationship between farm size and productivity emerges within the 5 to 70 hectare range of farm sizes. Across virtually all measures of productivity, farms between 20 and 70 hectares are found to be substantially more productive than farms under hectares. When the analysis is confined to fields cultivated to maize (Kenya's main food crop) the productivity advantage of relatively large farms stems at least partially from differences in technical choice related to mechanization, which substantially reduces labor input per hectare, and from input use intensity.
Keywords: Africa, agriculture, farm size, inverse relationship, Kenya, medium-scale farms, productivity.
七、技术采用的决定因素、成本效益分析，以及高附加值农业产业的发展
Technology adoption, capital deepening, and international productivity differences
技术应用、资本深化与国际生产率差异
Chaoran Chen
York University
Abstract: I document that cross-country differences in capital intensity are much larger in the agricultural sector than in the nonagricultural sector. To explain this fact, I build a model featuring technology adoption with fixed costs among heterogeneous farmers. More productive farmers operating larger farms pay the fixed cost and adopt a modern capital-intensive technology, while less productive ones choose a traditional labor-intensive technology. The model is calibrated using historical data on farmer adoption of mechanized technology in postwar America. This calibrated model is then employed to perform cross-country comparisons. Incorporating a technology adoption channel not only allows the model to predict substantial differences in agricultural capital intensity between rich and poor countries that an otherwise identical model would fall short in generating, but also improve explanatory power for cross-country agricultural productivity differences by 1.5-fold.
Keywords: Agricultural Productivity, Technology Adoption, Capital Intensity, Mechanization, Structural Transformation.
Trade and agricultural technology adoption: Evidence from Africa
贸易与农业技术应用：来自非洲的证据
Obie Porteous
Middlebury College
Abstract: The incentives for and effects of widespread technology adoption depend on the trade costs separating producers from input and output markets. I incorporate the decision to adopt imported fertilizer into a model of agricultural trade between 230 regional markets across sub-Saharan Africa. I then evaluate two alternative approaches to promoting technology adoption: lowering trade costs and subsidizing fertilizer. Whereas trade cost reduction shifts production towards the most productive regions, subsidies lead to larger increases in fertilizer use. Greater adoption lowers local food prices under existing high trade costs but only increases farmer incomes when trade costs are low.
Keywords: technology adoption, trade costs, input subsidies, fertilizer, Africa
八、在发达与欠发达国家中农村基础设施、农产品市场的可得性与弱势群体（儿童、妇女、老人）的营养健康的关系
Rural food markets and child nutrition
农村食品市场与儿童营养
Derek Headeyᵃ, Kalle Hirvonenᵇ, John Hoddinottᶜ, and David Stifelᵈ
ᵃᵇ International Food Policy Research Institute
ᶜ Cornell University
ᵈ Lafayette College
Abstract: Child dietary diversity is poor in much of rural Africa and developing Asia, prompting significant efforts to leverage agriculture to improve diets. However, growing recognition that even very poor rural households rely on markets to satisfy their demand for nutrient-rich non-staple foods warrants a much better understanding of how rural markets vary in their diversity, competitiveness, frequency and food affordability, and how such characteristics are associated with diets. This article addresses these questions using data from rural Ethiopia. Deploying a novel market survey in conjunction with an information-rich household survey, we find that children in proximity to markets that sell more non-staple food groups have more diverse diets. However, the association is small in absolute terms; moving from three non-staple food groups in the market to six is associated with an increase in the number of non-staple food groups consumed by 0.27 and the likelihood of consumption of any non-staple food group by 10 percentage points. These associations are similar in magnitude to those describing the relationship between dietary diversity and household production diversity; moreover, for some food groups, notably dairy, we find that household and community production of that food is especially important. These modest associations may reflect several specific features of our sample which is situated in very poor, food-insecure localities where even the relatively better off are poor in absolute terms and where, by international standards, relative prices for non-staple foods are very high.
Keywords: Food market diversity, child nutrition, diet diversity, Ethiopia.
Institutions, implementation, and program effectiveness: Evidence from a randomized evaluation of computer-assisted learning in rural China
机构、实施与项目有效性：来自中国农村电脑辅助学习的随机估计证据
Di Moᵃ, Yu Baiᵇ, Yaojiang Shiᶜ, Cody Abbeyᵃ, Linxiu Zhangᵈᵉ, Scott Rozelleᵃ, and Prashant Loyalkaᵃ
ᵃ Stanford University, USA
ᵇ Minzu University of China, China
ᶜ Shaanxi Normal University, China
ᵈ Chinese Academy of Sciences, China
ᵉ UNEP-International Ecosystem Management Partnership, China
Abstract: There is limited evidence on the degree to which differences in implementation among institutions matter for program effectiveness. To examine this question, we conducted an experiment in rural China in which public schools were randomly assigned to one of three treatments: a computer-assisted learning program (CAL) implemented by a government agency, the same program implemented by an NGO, and a pure control. Results show that compared to the pure control condition and unlike the NGO program, the government program did not improve student achievement. Analyzing impacts along the causal chain, we find that government officials were more likely to substitute CAL for regular instruction (contrary to protocol) and less likely to directly monitor program progress. Correlational analyses suggest that these differences in program implementation were responsible for the lack of impacts.
Keywords: Computer-assisted learning; education; external validity of program; implementation by government; randomized controlled trial
九、气候变化带来的农业生产风险识别，农村人口生活影响与适应性策略研究
Climate change and adaptation in agriculture: Evidence from US cropping patterns
气候变化与农业适应：来自美国种植方式的证据
Xiaomeng Cui
Abstract: Understanding how a changing climate alters regional comparative advantage is crucial for evaluating the economic impacts of climate change. I exploit temporal variation in decades-long averages of weather and estimate crop acreage elasticities with respect to climate change in the United States. I find substantial climate change adaptation through acreage adjustments in US agriculture. Climate change explains about 10-35% of the observed US corn and soybean expansion over the past 30 years, and climate-driven crop substitution has played an important role. The acreage response is heterogeneous across major and minor producing areas and across dryland and irrigated counties. (JEL classification: Q11, Q15, Q54)
Keywords: climate change, adaptation, comparative advantage, acreage elasticities, crop substitution
十、环境约束与农业发展问题的矛盾与协调（发展中国家为主）
Fertilizing growth: Agricultural inputs and their effects in economic development
化肥使用的增长：农业投入及其对经济发展的影响
John W. McArthurᵃ, Gordon C. McCordᵇ
ᵃ Brookings Institution, United Nations Foundation
ᵇ University of California, San Diego
Abstract: This paper estimates the role of agronomic inputs in cereal yield improvements and the consequences for countries' processes of structural change. The results suggest a clear role for fertilizer, modern seeds and water in boosting yields. We then test for respective empirical links between agricultural yields and economic growth, labor share in agriculture and non-agricultural value added per worker. The identification strategy includes a novel instrumental variable that exploits the unique economic geography of fertilizer production and transport costs to countries' agricultural heartlands. We find a half ton increase in staple yields generates a 14 to 19 percent higher GDP per capita and a 4.6 to 5.6 percentage point lower labor share in agriculture five years later. The results suggest a strong role for agricultural productivity as a driver of structural change.
Keywords: agriculture, fertilizer, structural change, growth, green revolution.
十一、各类环保政策效果的评估，包括政策成本和环保的等价经济收益评估
The effect of the conservation reserve program on rural Economies: Deriving a statistical verdict from a null finding
保护性储备计划对农村经济的影响：从无效结果中得出的统计结论
Jason P. Brownyᵃ, Dayton M. Lambertzᵇ, Timothy R. Wojanxᶜ
ᵃ Federal Reserve Bank of Kansas City
ᵇ University of Tennessee Institute of Agriculture
ᶜ USDA, Economic Research Service
Abstract: This article suggests two methods for deriving a statistical verdict from a null finding, allowing economists to more confidently conclude when \not significant" can in fact be interpreted as no substantive effect." The proposed methodology can be extended to a variety of empirical contexts where size and power matter. The example used to demonstrate the method is the Economic Research Service's 2004 Report to Congress that was charged with statistically identifying any unintended negative employment consequences of the Conservation Reserve Program (the Program). The report failed to identify a statistically significant negative long-term effect of the Program on employment growth, but the authors correctly cautioned that the verdict of no negative employment effect" was only valid if the econometric test was statistically powerful. We replicate the 2004 analysis and use new methods of statistical inference to resolve the two critical deficiencies that preclude estimation of statistical power by economists: 1) positing a compelling effect size, and 2) providing an estimate of the variability of an unobserved alternative distribution using simulation methods. We conclude that the test used in the report had high power for detecting employment effects of -1 percent or lower resulting from the Program, equivalent to job losses reducing a conservative-estimate of environmental benefits by a third.
Keywords: power analysis, Monte Carlo simulation, hypothesis testing
十二、水资源管理的政策创新、水市场发展和效果评估
What is the use value of irrigation water from the high plains aquifer?
高平原含水层的灌溉水的使用价值是什么？
Federico Garcia Suarezᵃ, Lilyan E. Fulginitiᵇ, and Richard K. Perrinᶜ
ᵃ Universidad de la Republica, Uruguay
ᵇᶜ University of Nebraska, Lincoln
Abstract: This study provides an estimate of the gross value of irrigation water from the U.S. High Plains Aquifer. We estimate a yield function for aggregated crop biomass production, based on county-level observations for 1960–2007. This study found that irrigation increases total biomass yield in this region by an average of 51%. We estimate the average gross annual value of irrigation as of 2007 to be $196 per acre, for a total of about $3 billion across the aquifer. We also estimate that on average across the aquifer, exposure to 24 hours of temperatures above 33C (one degree day) reduces biomass yield by 3%, with a value in 2007 of about $10 per acre.
Keywords: Groundwater, High Plains Aquifer, irrigation response, production function, yields.
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