学术前沿 | 《American Journal of Agricultural Economics》近期农经主题文章汇总

2020年《American Journal of Agricultural Economics》的影响因子为4.082，在经济学期刊中排名第62。

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亚洲

How Does Straw Burning Affect Urban Air Quality in China?

Volume 103, Issue 3 

May 2021

作者：Shiqi Guo（Shanghai Jiao Tong University）

Abstract：Over the past decade, straw burning has been debated as one of the causes of severe air pollution in developing countries. However, the magnitude and pattern of its impact on air quality have not been precisely estimated. This study employs remote sensing data on straw fires from different satellite sources and examines its overall impact on urban air quality in China. Exploiting daily variations in straw burning activities and air pollution with a difference‐in‐differences strategy across 290 cities and 620 days, I find a clear temporal pattern for the straw burning effect. On the first day after burning, the index of air pollution increases by 6.5 in urban areas, equivalent to 9.4% of the mean. This impact decreases over time and remains significant for at least eight days. The effect is larger for fires located in the upwind direction relative to urban areas and is limited with lower wind speed. In terms of distance, pollution is mostly driven by straw fires within 100 km from urban centers but could also be influenced by fires as far as 600 km away. Among different pollutants, particulate matters are increased most by straw fires. The effect is largest and most persistent in October and November, when straw burning prevails in the north after harvest, but is also non‐negligible in other seasons.

keywords：Agricultural fire;air pollution;China;straw burning

China's Missing Pigs: Correcting China's Hog Inventory Data Using a Machine Learning Approach

Volume 103, Issue 3 

May 2021

作者：Yongtong Shao（Tianjin University of Commerce）；Tao Xiong（Huazhong Agricultural University）；Minghao Li（New Mexico State University）；Dermot Hayes（Department of Economics and the Center for Agricultural and Rural Development at Iowa State University）；Charles F（Department of Economics and the Center for Agricultural and Rural Development at Iowa State University）；Wendong Zhang（Department of Economics and the Center for Agricultural and Rural Development at Iowa State University）；Wei Xie（Tianjin University of Commerce）

Abstract：Small sample size often limits forecasting tasks such as the prediction of production, yield, and consumption of agricultural products. Machine learning offers an appealing alternative to traditional forecasting methods. In particular, support vector regression has superior forecasting performance in small sample applications. In this article, we introduce support vector regression via an application to China's hog market. Since 2014, China's hog inventory data has experienced an abnormal decline that contradicts price and consumption trends. We use support vector regression to predict the true inventory based on the price‐inventory relationship before 2014. We show that, in this application with a small sample size, support vector regression outperforms neural networks, random forest, and linear regression. Predicted hog inventory decreased by 3.9% from November 2013 to September 2017, instead of the 25.4% decrease in the reported data.

keywords：China;machine learning;prediction;pork;support vector regression

Farmers, Traders, and Processors: Buyer Market Power and Double Marginalization in Indonesia

Volume 103, Issue 2 

March 2021

作者：Thomas Kopp（University of Siegen；Research Center Pluralist Economics and the Center for Economic Education in Siegen）；Richard J. Sexton（University of California，Davis ；University of California Giannini Foundation of Agricultural Economics）

Abstract：Buyer market power can significantly reduce farm prices and incomes, making curtailment of such power a key strategy to improve rural livelihoods in emerging economies. A “double marginalization problem” occurs when market power is exercised at multiple stages in a supply chain. Although double marginalization has been studied extensively from a seller‐power perspective, the corresponding problem on the buyer‐power side has received scant attention. This paper addresses that lacuna through developing a vertical market model that allows buyer power to be exercised in local farmer–trader markets and also downstream at the trader–processor stage. We derive equilibrium results for output, prices, and economic welfare under alternative competition scenarios. The model is applied to the Indonesian rubber value chain by estimating the magnitude of buyer market power in farmer–trader and trader–processor interactions and quantifying the extent of welfare loss and redistribution of income among market participants due to double marginalization. Standard theory for seller double marginalization posits that it should be eliminated through vertical coordination within the supply chain. We conclude by discussing why such coordination may not occur within emerging‐economy supply chains and considering policy innovations to facilitate better coordination.

keywords：Double marginalization;Indonesia;market power;oligopsony

The Impacts of GM Foods: Results from a Randomized Controlled Trial of Bt Eggplant in Bangladesh

Volume 103, Issue 4 

August 2021

作者：Akhter U. Ahmed（International Food Policy Research Institute, Dhaka Bangladesh）；John Hoddinott（International Food Policy Research Institute, Dhaka Bangladesh）；Cornell University（International Food Policy Research Institute, Dhaka Bangladesh）；Naveen Abedin（International Food Policy Research Institute, Dhaka Bangladesh）；Nusrat Hossain（International Food Policy Research Institute, Dhaka Bangladesh）

Abstract：We implemented a cluster randomized controlled trial to assess the impact of genetically modified eggplant (Bt brinjal) in Bangladesh. Our two primary outcomes were changes in yield and in pesticide costs. Cultivation of Bt brinjal raises yields by 3,564 kg/ha. This statistically significant impact is equivalent to a 51% increase relative to the control group. There is a statistically significant fall in pesticide costs, 7,175 Taka per hectare (85 USD per ha), a 37.5% reduction. Yield increases arise because Bt farmers harvest more eggplant and because fewer fruits are discarded because they are damaged. Bt brinjal farmers sell more eggplant and receive a higher price for the output they sell while incurring lower input costs, resulting in a 128% increase in net revenues. Bt brinjal farmers used smaller quantities of pesticides and sprayed less frequently. Bt brinjal reduced the toxicity of pesticides as much as 76%. Farmers growing Bt brinjal and who had pre‐existing chronic conditions consistent with pesticide poisoning were 11.5% points less likely to report a symptom of pesticide poisoning and were less likely to incur cash medical expenses to treat these symptoms. Our results are robust to changes in model specification and adjustment for multiple hypothesis testing. We did not find evidence of heterogeneous effects by farmer age, schooling, or land cultivated. Bt brinjal is a publicly developed genetically modified organism that conveys significant productivity and income benefits while reducing the use of pesticides damaging to human and ecological health.

keywords：Bangladesh;eggplant;GMOs;pesticides;yield

北美洲

The Rationality of USDA Forecasts under Multivariate Asymmetric Loss

Volume 103, Issue 3 

May 2021

作者：Siddhartha S. Bora（The Ohio State University: Columbus, Ohio, US）；Ani L. Katchova（Ohio State University: Columbus, OH, US）；Todd H. Kuethe（Purdue Universtiy: West Lafayette, Indiana, US）

Abstract：A large number of previous studies suggest that many USDA forecasts are biased and/or inefficient. These findings, however, may be the result of the assumed loss function of USDA forecasters. We test the rationality of the USDA net cash income forecasts and the WASDE production and price forecasts between 1988 and 2018 using a flexible multivariate loss function that allows for asymmetric loss and non‐separable forecast errors. Our results provide robust evidence that USDA forecasters are rational expected loss minimizers yet demonstrate a tendency to place a greater weight on under‐ or overprediction. As a result, this study provides an alternate interpretation of previous findings of forecast irrationality.

keywords：asymmetric loss;fixed‐event forecasts;forecast rationality;net cash income

Oil Price Pass through to Agricultural Commodities

Volume 103, Issue 2 

March 2021

作者：Clark Lundberg（San Diego State University, San Diego, California, USA）；Tristan Skolrud（Department of Agricultural and Resource Economics, University of Saskatchewan, Saskatoon, Canada）；Bahram Adrangi（Pamplin School of Business, University of Portland, Portland, Oregon）；Arjun Chatrath（Pamplin School of Business, University of Portland, Portland, Oregon）

Abstract：Energy represents an important share of production costs for many agricultural commodities. Previous studies have found mixed evidence of a pass‐through relationship between oil prices and agricultural commodity prices, a relationship that has the potential to disrupt farm‐level decision making. We propose that these mixed findings are in part due to heterogeneity in the pass‐through relationship across time horizons. We use a new wavelet‐based regression approach to explore horizon‐based heterogeneity in the relationship between oil and agricultural commodity prices. We find strong evidence of heterogeneity across time horizons and commodities. We develop a stylized model of agricultural production and show that agricultural contracts can generate price stickiness that leads to heterogeneity in input price pass through over different horizons. We also find evidence that recent technological shifts have led to a structural change in this horizon‐based heterogeneity.

keywords：Agricultural commodities;horizons;oil prices;price transmission;wavelets

Microclimate Engineering for Climate Change Adaptation in Agriculture: The Case of California Pistachios

Volume 103, Issue 4 

August 2021

作者：Itai Trilnick（Department of Agricultural and Resource Economics, UC Berkeley）；David Zilberman（Agricultural and Resource Economics, UC Berkeley）

Abstract：Can farmers adapt to climate change by altering effective weather conditions on their fields? Existing technologies allow farmers to cool down plants by a few degrees during critical periods, reducing the damage from excess heat. With nonlinear effects of high temperatures on yields, slight cooling can bring significant gains in many crops. We call this approach “microclimate engineering” (MCE) and note that it could be useful as a climate change adaptation concept. Our case study deals with California pistachios, threatened by warming daytime temperatures in the winter. A new solution for sunlight reflection, based on products already used in other contexts and crops, could potentially help deal with this challenge. We develop a model to analyze grower choice and market outcomes with MCE for California pistachios. The expected increase in welfare for the period of 2020–2040 is assessed at 0.49–1.42 billion dollars under several scenarios. Simulation results show increases in consumer surplus and total welfare when MCE is available but decreases in aggregate grower profits. We also introduce market power to test its potential effects on the gains from MCE, finding mixed effects.

keywords：Agriculture;climate change;kaolin;microclimate engineering;pistachio

Piecemeal Farm Regulation and the U.S. Commerce Clause

Volume 103, Issue 3 

May 2021

作者：Colin A. Carter（University of California）；K. Aleks Schaefer（Michigan State University）；Daniel Scheitrum（University of Arizona）

Abstract：Since January 2015, California has required that all shell eggs consumed in the state be produced cage free or by hens housed in enlarged cages defined under Assembly Bill 1437. This paper assesses the effects of California farm animal housing restrictions on egg prices and production practices inside and outside California, and on the volume of interstate trade. We find that the California regulation generated short‐ and long‐run egg price increases across the U.S. It has also bifurcated production methods outside California yielding more concentrated interstate trade. The largest share of the associated private costs was borne by out‐of‐state consumers. The balance between a state's power to regulate food production within its borders and the impacts on out‐of‐state producers and consumers has potential legal implications under the dormant Commerce Clause of the U.S. Constitution.

keywords：dormant Commerce;Clause eggs;farm animal;welfare food movement;interstate trade

Field-Level Land-Use Adaptation to Local Weather Trends

Volume 103, Issue 4 

August 2021

作者：Steven M. Ramsey（Research Agricultural Economist, Markets and Trade Economics Division, Economic Research Service, U.S. Department of Agriculture, Kansas City, MO. Jason S）；Jason S. Bergtold（Department of Agricultural Economics, Kansas State University, Manhattan, KS）；Jessica L. Heier Stamm（Department of Industrial and Manufacturing Systems Engineering, Manhattan, Kansas）

Abstract：The intersection of agriculture and climate has been well researched for at least the last couple of decades. Largely, the motivation for previous research has been the potential impact on food security for the world's (growing) population. Many studies have predicted unfavorable yield scenarios for some geographic regions. As a result, another common research theme is farmer adaptation to a changing climate. Typically, these studies are concerned with what farmers could or should do to adapt to adverse outcomes. However, research examining whether farmers respond to weather patterns has largely been ignored. Answering this question can help provide more accurate food security analyses: if farmers do respond to changing patterns through cropping decisions, for instance, the global food supply outcome will be different than a world in which they do not respond. This article aims to provide insights into what and how farmers' cropping decisions respond to weather patterns. The study region is a set of eleven Kansas counties. The article provides an important step toward more credible estimates of global food supplies under changing climates and the methods themselves translate to other areas. Results suggest that land-use responses to changing weather patterns will vary across time and space.

keywords：Adaptation agriculture climate change;crop choice;Kansas weather

Peers in the Field: The Role of Ability and Gender in Peer Effects among Agricultural Workers

Volume 103, Issue 3 

May 2021

作者：Alexandra E. Hill（Colorado State University, Fort Collins, CO）；Jesse Burkhardt（Colorado State University, Fort Collins, CO）

Abstract：This article presents evidence on peer effects among U.S. agricultural workers. On average, we find that a 10% increase in peer productivity increases focal worker productivity by 2.8%. This effect is modified by the ability and gender of workers and peers. Exceptionally slow workers are least responsive to peers and have pronounced negative spillovers on the productivity of their coworkers—their presence decreases productivity by 2%. Male workers are more responsive to their peers than female workers—a 10% increase in peer productivity increases the productivity of men by 3% and women by 2.6%. Workers are also generally more responsive to peers of similar ability and gender. Workers increase their speed the most when in the presence of peers with abilities just above their own. Male workers are more responsive to male peers than female peers, and female workers are more responsive to female peers.

keywords：Agricultural workers;social spillovers;superstars

Resilience in “Flash Events” in the Corn and Lean Hog Futures Markets

Volume 103, Issue 2 

March 2021

作者：Xinyue He（University of Illinois at Urbana-Champaign）；Teresa Serra（University of Illinois at Urbana-Champaign）；Philip Garcia（University of Illinois at Urbana-Champaign）

Abstract：The Commodity Futures Trading Commission (CFTC) recently identified large intra-day price changes or “flash events” in continuously traded commodity futures markets. These flash events fueled discussion on whether futures markets are becoming less effective as human intervention is diminishing in favor of automated trading. Using intra-day data, we examine liquidity resilience during “flash events” in corn and lean hog futures markets from 2014 to 2019. Overall, we find little evidence that the liquidity provision in these two markets relative to normal days becomes fragile when large price movements occur. Our analysis suggests that flash events are heavily influenced by unanticipated changes in fundamentals that may lead to a new equilibrium price. Liquidity dynamics during these events supports the view that active market making helps absorb the increased volume and stabilize markets.

keywords：Depth flash events;futures markets;liquidity costs;quoted spread resilience

The Effect of Land Use Restrictions Protecting Endangered Species on Agricultural Land Values

Volume 103, Issue 1 

January 2021

作者：Melstrom Richard T.（Institute of Environmental Sustain-ability, Loyola University Chicago, Chicago, Illinois）

Abstract：This article examines the effect of U.S. Endangered Species Act (ESA) regulations on agricultural values. Agricultural development is an important contributor to habitat and biodiversity loss in the United States. The ESA attempts to limit this loss by prohibiting habitat destruction on private lands,but this practice is controversial because it places much of the burden for conservation on farmers. I measure the effect of these restrictions on agriculture using a hedonic analysis of county-level agricultural land values, profits, and revenues reported in the last four rounds of the agricultural census.Results provide strong evidence that ESA regulations depress these three economic measures in dryland areas, which includes counties with less than 1% of agricultural land in irrigation. Specially, Ifind that farmland value and profit decline 4% after listing on average at the county level in dryland areas with protected habitat. There is no evidence that values are affected in irrigated counties.

keywords：Environmental policy;land markets;property values

Environmental Externalities from Agriculture: Evidence from Water Quality in the United States

Volume 103, Issue 1 

January 2021

作者：Paudel Jayash（Department ofEconomics at Boise State University）；Crago Christine L（Department of Resource Economics at the Uni-versity of Massachusetts Amherst）

Abstract：Agricultural fertilizer use is widely acknowledged to be a leading cause of water pollution. Yet, no national estimates exist on the effect of fertilizer application on concentrations of agricultural pollutants in US watersheds. This paper employs a watershed‐level panel data on nitrogen and phosphorus pollution readings to examine the impact of fertilizer use on US water quality over a fifty‐five‐year time period from 1951 to 2005. Findings show that a 10% increase in the use of nitrogen and phosphorus fertilizers leads to a 1.52% increase in the concentration of nitrogen and a 1.37% increase in the concentration of phosphorus across watersheds. Results also indicate that there exists heterogeneity in nutrient pollution elasticity estimates across eighteen US water resource regions, ranging from 0.082 to 0.733 in the case of nitrogen and from 0.036 to 0.475 in the case of phosphorus. Combining our results with prior hydrology‐based studies, we find that a 100% increase in the use of nitrogen fertilizers in the Lower Mississippi water resource region expands the size of the hypoxic zone in the Gulf of Mexico by roughly 3,389 square miles, equivalent to about two‐fifths of the estimated size of the dead zone in the Gulf of Mexico.

keywords：Agricultural runoff;environmental effects;fertilizers; nitrogen;phosphorus;United States;water pollution

Hog Barns and Neighboring House Prices: Anticipation and Post‐Establishment Impacts

Volume 103, Issue 3 

May 2021

作者：Chad Lawley（Department of Agribusiness and Agricultural Economics）

Abstract：The impact of large‐scale hog barns on residential property values is at the forefront of local concerns about livestock development. In this article, I examine the impact of hog barns on house prices in an intensive production region of Manitoba, Canada. Timing of barn establishment and precise locations of houses and barns are used to gain a better understanding of the dynamic impacts of hog barns on house prices. I find that houses within 2 km of a hog barn sell for 5.7% less than similar houses located a little farther away from a barn. Quasi‐myopic specifications indicate that house prices fall by 6.2% up to three years prior to barn establishment, consistent with market anticipation of the future location of hog barns. Accounting for anticipation increases the post‐establishment discount to 8%, suggesting that ignoring anticipation of new barn establishment biases estimated post‐establishment impacts downwards.

keywords：Air quality;anticipation;disamenity;hedonic pricing;intensive livestock;property values

非洲

How Do Farmers Learn from Extension Services? Evidence from Malawi

Volume 103, Issue 2 

March 2021

作者：Annemie Maertens（Sussex University）；Hope Michelson（University of Illinois at Urbana-Champaign）；Vesall Nourani（MIT）

Abstract：Though extension services have long since proved their value to agricultural production and farmer prosperity, their record in sub‐Saharan Africa has been mixed. To study the impact of such programs on farmers' learning about agricultural technologies, we implemented a quasi‐randomized controlled trial and collected detailed panel data among Malawian farmers. Based on those findings, we develop a two‐stage learning framework, in which farmers formulate yield expectations before deciding on how much effort to invest in learning about these processes. Using data centered on farmer beliefs, knowledge, and constraints, we find evidence that beliefs about potential yields hinge on first‐hand and local experience, and that these beliefs significantly impact learning efforts. Consistent with this, we find that farmers who participated in season‐long, farmer‐led demonstration plot cultivation plan to adopt more components of new multi‐component technology, compared to farmers who were invited to attend only field‐day events.

keywords：Agricultural extension;Learning;sub‐Saharan Africa

Improved Drying and Storage Practices that Reduce Aflatoxins in Stored Maize: Experimental Evidence from Smallholders in Senegal

Volume 103, Issue 1 

January 2021

作者：Bauchet Jonathan（Department of Hospitalityand Tourism Management at Purdue University）；Prieto Stacy（With Catholic Relief Services）；RickerGilbert Jacob （department of Agricultural Economics at Purdue Univer-sity）

Abstract：Proper post‐harvest treatment of crops is key to limiting contamination by aflatoxins, potent carcinogens, but little is known about constraints to adoption of best post‐harvest practices among smallholder farmers in developing countries. We use a randomized controlled trial with 2,000 maize producers in Senegal to test whether low awareness and/or lack of drying and storage technologies are barriers to storing safe maize. A novel feature of our intervention is that we offered both drying and storage technologies to farmers and evaluated their combined impact. We found that only hermetic (airtight) storage bags caused a statistically significant reduction in total aflatoxin levels after 3–4 months of storage, reducing the likelihood that maize had total aflatoxin levels above safe‐to‐eat thresholds by 30%. Our results provide practical guidance to lower aflatoxins in staple crops and suggest that strategies to reduce aflatoxins should address issues from harvest to storage in a comprehensive manner.

keywords：aflatoxins;grain drying; hermetic bag;improved storage technology;PICS;post-harvest;practices;Senegal;sub-Saharan Africa

Links between Maternal Employment and Child Nutrition in Rural Tanzania

Volume 103, Issue 3 

May 2021

作者：Bethelhem Legesse Debela（University of Goettingen）；Esther Gehrke（Agricultural Economics and Rural Policy Group, Wageningen University and Research）；Matin Qaim（University of Goettingen, Germany）

Abstract：Improving child nutrition and empowering women are two important and closely connected development goals. Fostering female employment is often seen as an avenue to serve both these goals, especially if it helps to empower the mothers of undernourished children. However, maternal employment can influence child nutrition through different mechanisms, and the net effect may not necessarily be positive. We develop a theoretical model to show that maternal employment can affect child nutrition through changes in income, intrahousehold bargaining power, and time available for childcare. The links are analyzed empirically using panel data from farm households in rural Tanzania. We find that the links between maternal employment and child height‐for‐age Z‐scores (HAZ) are non‐linear. Off‐farm employment is negatively associated with child HAZ at low levels of labor supply. The association turns positive at higher levels of labor supply and negative again at very high levels. The associations between maternal on‐farm work and child nutrition are weaker and not statistically significant. These findings can help to better design development interventions that foster synergies and avoid potential tradeoffs between female empowerment and child nutrition goals.

keywords：Child nutrition;female employment;stunting;Tanzania;women's empowerment

Climate‐Smart Innovations and Rural Poverty in Ethiopia: Exploring Impacts and Pathways

Volume 103, Issue 3 

May 2021

作者：Wondimagegn Tesfaye（UNU-MERIT and Maastricht University）；Garrick Blalock（Cornell University）；Nyasha Tirivayi（UNU-MERIT and Maastricht University）

Abstract：Climate‐smart innovations have been receiving increasing attention in policy dialogues for their potential to transform agricultural systems and improve the well‐being and resilience of farm households. Using recent panel data from Ethiopia combined with novel historical weather data, we provide microeconomic evidence of the welfare effects of conservation agriculture (CA), a climate‐smart agricultural practice. We use a panel data endogenous switching regression model to deal with selection bias and farmer heterogeneity in CA choice. The study finds that the CA practices that play a pivotal role in addressing the exigencies of rural poverty are minimum tillage, cereal‐legume intercropping, and their combination. These practices reduce the incidence and depth of poverty in areas prone to rainfall stress, which is an indication of their risk mitigation role. In contrast, crop residue retention and its combination with minimum tillage appear not to be economically attractive CA options. The results show that CA portfolios that include minimum tillage and cereal‐legume associations can accelerate efforts to reduce rural poverty and improve climate risk management. We caution against exaggerated expectations of CA's economic benefits and a rigid recommendation of CA.

keywords：conservation agriculture;Ethiopia;farm heterogeneity;panel endogenous switching regression;poverty

Rainfall Variability, Child Labor, and Human Capital Accumulation in Rural Ethiopia

Volume 103, Issue 3 

May 2021

作者：Jonathan Colmer（University of Virginia, Charlottesville, Virginia）

Abstract：How does income uncertainty affect human capital investments in agrarian economies? Using child‐level panel data, I exploit a medium‐run change in mean‐preserving rainfall variability to identify the effects of income uncertainty on the child labor decisions and human capital investments of smallholder farmers in rural Ethiopia. I estimate that increased rainfall variability is associated with less child labor and more schooling, consistent with a diversification mechanism. These findings highlight the empirical relevance of income uncertainty for decision making and household investment in rural economies. I find no evidence that rainfall variability is associated with past, present, or future rainfall, nor with income, wealth, and agricultural outcomes. As such, residual variation in realized income shocks—the main confounding interpretation—does not appear to explain the results.

keywords：Child labor;human capital;income uncertainty;rainfall variability

Infrastructure Improvements and Maize Market Integration: Bridging the Zambezi in Mozambique

Volume 103, Issue 2 

March 2021

作者：Sam Jones（UNU-WIDER, Mozambique）；César Salazar（University of Bío-Bío）

Abstract：Historically, transport infrastructure connecting the most agriculturally productive areas of Mozambique and the richer southern region has been poor. A primary bottleneck was an unreliable ferry service over the Zambezi river, addressed by construction of a road bridge in 2009. In this paper we identify the impact of this transport infrastructure enhancement on integration of national maize markets. Applying a dyadic regression approach, we find a significant narrowing of equilibrium price differences among market pairs that experienced a large relative reduction in journey times due to the new bridge. We also estimate that the elasticity of the absolute price differential with respect to intermarket driving times is around 30%. As such, the new bridge infrastructure enhanced market integration by shrinking the “internal border” at the river, but such benefits were spatially limited.

keywords：agricultural market;performance infrastructure;natural experiment prices

One Size Fits All? Experimental Evidence on the Digital Delivery of Personalized Extension Advice in Nigeria

Volume 103, Issue 2 

March 2021

作者：Aminou Arouna（Africa Rice Centre (AfricaRice)）；Jeffrey D. Michler（Africa Rice Centre (AfricaRice)）；Wilfried G. Yergo（Africa Rice Centre (AfricaRice)）；Kazuki Saito（Department of Agricultural and Resource Economics, University of Arizona, Tucson, USA）

Abstract：Blanket advice on optimal fertilizer application rates has failed to achieve potential yield gains for crop production in much of Sub‐Saharan Africa. However, digital technology now makes it possible to deliver personalized extension services to farmers at a much lower cost. We present results from a randomized control trial designed to evaluate the effectiveness of a mobile application that provides personalized advice on rice nutrient management. We find that households who were just given the personalized advice increase their yield by 7% and increase their profit by 10%. On average, personalized advice increases yields without increasing the overall quantity of fertilizer used. We conclude that the scaling of personalized extension services could improve productivity and livelihoods in Sub‐Saharan Africa without necessarily increasing the total amount of fertilizer in use.

keywords：decision support tools;extension;information and communication technology;information interventions;RiceAdvice

Does Aversion to Price Risk Drive Migration? Evidence from Rural Ethiopia

Volume 103, Issue 4 

August 2021

作者：Yu Na Lee（University of Guelph）

Abstract：I investigate whether a rural household's aversion to commodity price volatility drives out‐migration. Adapting the standard agricultural household framework, I model a rural household's migration decision making under uncertainty in commodity prices and migrant wages. Empirical results indicate that a greater household‐level aversion to price risk is significantly related to a higher likelihood of out‐migration. Moreover, the significant relationship between aversion to price risk and migration is more pronounced in villages that lack daily markets and food aid, implying that the negative welfare effects of food price volatility may be amplified by underdeveloped market mechanisms and poor local infrastructure. A battery of robustness checks and falsification tests provide strong suggestive evidence to conclude that migration is a household strategy to manage price risk. This article is among the first to highlight the link between price risk and migration, and complements the literature on income risk and migration.

keywords：Commodity price;Ethiopia;migration;price volatility;risk;uncertainty

Income Variability, Evolving Diets, and Elasticity Estimation of Demand for Processed Foods in Nigeria

Volume 103, Issue 4 

August 2021

作者：Alan de Brauw（International Food Policy Research Institute (IFPRI)）；Sylvan Herskowitz（International Food Policy Research Institute (IFPRI)）

Abstract：We present evidence on evolving dietary patterns in Nigeria using six rounds of household consumption data from the Nigerian General Household Survey panel between 2011 and 2016. First, following conventional definitions in the literature, we show that Nigeria has not shown any aggregate increase in consumption of highly processed foods over this period, contrary to patterns observed elsewhere in the region. In fact, consumption of highly processed foods at home has declined, while food consumed away from home, often assumed to be highly processed, has risen substantially. We then show that estimates of food expenditure elasticities of different food types are highly sensitive to different estimation approaches and raise concerns about some frequently used methods in the literature. In the absence of credible exogenous variation, we argue for the importance of panel methods and household fixed effects to control for time invariant factors likely to confound cross‐sectional estimates. Finally, we examine semiparametric Engel curves for different food groups and find that apparent curvature in the relationships between food budget shares and overall food expenditure levels in the raw data become nearly linear when removing variation explained by time‐invariant household factors.

keywords：Demand elasticities;elasticity estimation methods; Engel curves;Nutrition;Processed foodsI

Water, Policy, and Productivity in Egyptian Agriculture

Volume 103, Issue 4 

August 2021

作者：Keith Fuglie（United States Department of Agriculture）；Boubaker Dhehibi（International Center for Agricultural Research in the Dry Areas (ICARDA)）；Ali Ahmed Ibrahim El Shahat；Aden Aw-Hassan（Consultative Group on International Agricultural Research）

Abstract：zWhen water scarcity restricts agricultural production, expanding water resources is only one option to increase or maintain output; investments in research to raise productivity can also release constraints on growth. In this paper, we construct a model of optimal resource allocation with both public and private inputs in production—the public sector invests in research and irrigation infrastructure to supply technology and water, respectively, whereas the private sector supplies other inputs. The model is used to derive shadow values for water that suggest “crop per drop” valuations are likely to significantly overstate the marginal value of water in agriculture. We apply our model to analyze sources of growth in Egyptian agriculture, which is almost entirely dependent on publicly supplied irrigation water, over 1961–2016. We construct two indexes of total productivity: total factor productivity treats resources from a producer perspective, where water is free and resource rents accrue to land. Total resource productivity takes a social perspective, where government subsidies for irrigation are included as a cost of production, and resource rents are assigned to water withdrawals for agriculture. Our results find that technological innovations and efficiency gains contributed significantly more to agricultural growth in Egypt than expansion of irrigated area or water use. Productivity growth accelerated in the 1980s following the transition from a socialist to a market‐oriented economy. Including social costs of irrigation provision reduces the implied rate of total productivity growth only marginally. Nonetheless, the rise in total resource productivity significantly increased the value of natural resource rents in Egyptian agriculture.

keywords：Agricultural capital stock;aquaculture; growth accounting;irrigation and drainage;total factor productivity;total resource productivity;unit resource rent

Information and Communication Technologies to Provide Agricultural Advice to Smallholder Farmers: Experimental Evidence from Uganda

Volume 103, Issue 1 

January 2021

作者：Bjorn Van Campenhout（International Food Policy Research Institute (IFPRI)）；David J. Spielman（International Food Policy Research Institute (IFPRI)）；Els Lecoutere（University of Antwerp）

Abstract：Agricultural advisory services generally rely on interpersonal knowledge transfers by agricultural extension agents who visit farmers to provide information. This approach is not always effective and has proved hard to scale sustainably, particularly in highly dispersed smallholder farming systems. Information and communication technologies (ICTs) have been advanced as a promising way to overcome many of the problems associated with conventional agricultural extension. We evaluate the effectiveness of an ICT-mediated approach to deliver agricultural information in a field experiment conducted among small-scale maize farmers in eastern Uganda. Three complementary technologies designed to address both informational and behavioral constraints to technical change are considered. First, we investigate the effectiveness of audiovisual messages (video) as a means of delivering information on input use and improved maize management practices to farmers. Second, we quantify the additional impact of complementing video with an interactive voice response (IVR) service. Third, we estimate the incremental effect of time-sensitive short message services (SMS) messages designed to remind farmers about applying key practices at specific points during the season. We find that households that were shown a short video on how to become better maize farmers were performing significantly better on a knowledge test, more likely to apply recommended practices, and more likely to use fertilizer than households that did not view the video. These same households also reported maize yields about 10.5% higher than those that did not view the video. We find little evidence of an incremental effect of the IVR service or SMS reminders.

keywords：Agricultural extension;information and communication technology;interactive voice response;maize;short message services;Uganda;video

南美洲

Measurement Error Mechanisms Matter: Agricultural Intensification with Farmer Misperceptions and Misreporting

Volume 103, Issue 2 

March 2021

作者：Kibrom A. Abay（International Food Policy Research Institute）；Leah E. M. Bevis（Ohio State University）；Christopher B. Barrett（Applied Economics and Management at Cornell University）

Abstract：The mechanism(s) that generate measurement error matter for inference. Survey measurement error is typically thought to represent simple misreporting correctable through improved measurement. But errors might also or alternatively reflect respondent misperceptions that materially affect the respondent decisions under study. We show analytically that these alternate data generating processes imply different appropriate regression specifications and have distinct effects on the bias in parameter estimates. We introduce a simple empirical technique to generate unbiased estimates under more general conditions and to apportion measurement error between misreporting and misperceptions in measurement error when one has both self‐reported and objectively measured observations of the same explanatory variable. We then apply these techniques to the longstanding question of agricultural intensification: Do farmers increase input application rates per unit area as the size of the plots they cultivate decreases? Using nationally representative data from four sub‐Saharan African countries, we find evidence that measurement error in plot size reflects a mixture of farmer misreporting and misperceptions. The results matter for inference around the intensification hypothesis and call into question whether more objective, precise measures are always preferable when estimating behavioral parameters.

keywords：Agricultural inputs;Boserup;non‐classical measurement error;smallholders

Climate Adaptation and Conservation Agriculture among Peruvian Farmers

Volume 103, Issue 3 

May 2021

作者：Heleene Tambet（International Food Policy Research Institute）；Yaniv Stopnitzky（Department of Economics at the University of San Francisco）

Abstract：Peruvian agriculture will likely experience serious economic impacts of climate change, with changing rainfall and temperature patterns forcing farmers to confront abnormal climate conditions. In this context we study the impact of climate shocks on the agricultural practices of farmers who grow two main staples: maize and potato. We focus on four types of agricultural techniques: (a) those that reduce soil degradation, (b) those that conserve water, (c) the application of inorganic fertilizer, and (d) the application of pesticides and herbicides. We combine three rounds of cross‐sectional data from the Peru National Agricultural Survey with long‐term climate data to construct georeferenced shocks of abnormal rainfall levels and variation. Our empirical strategy controls for time‐invariant characteristics of small localities, secular time trends, and farmer and farm characteristics to estimate how shocks affect farmers' choices in subsequent growing cycles. Our findings show that: (a) farmers reduce soil conservation practices after one year of high rainfall, but multiple years of low rainfall increase adoption significantly; (b) the rate of pesticide use increases by eight percentage points following a drought year but is insensitive to multiple shock years; (c) water conservation measures are used less after high precipitation or when volatility was unusually low, and multiple years of insufficient rain tend to enhance this response; and (d) fertilizer use is less sensitive than other outcomes to weather fluctuations. These findings suggest that understanding how responsive farmers' practices are to weather shocks can inform policy design and help mitigate risks from changing weather patterns.

keywords：adaptation; agriculture;climate change;conservation

Weather Shocks and Labor Allocation: Evidence from Rural Brazil

Volume 103, Issue 4 

August 2021

作者：Danyelle Branco；José Féres（Instituto de Pesquisa Econômica Aplicada - IPEA）

Abstract：We examine the effects of rainfall shocks on household work decisions in Brazil. We show that rural farming households increase labor supply in non‐agricultural sectors during drought episodes. An additional drought month per year is associated with greater likelihood of holding more than one job, lower share of agricultural employment, and more time spent performing a secondary job. Together, these findings suggest that households alter their labor decisions to mitigate the consequences of weather shocks.

keywords：Agricultural households;drought shocks;labor allocation;Northeastern Brazil

欧洲

Modeling Corners, Kinks, and Jumps in Crop Acreage Choices: Impacts of the EU Support to Protein Crops

Volume 103, Issue 4 

August 2021

作者：Obafèmi P. Koutchadé（Agricultural Research (INRAE) in the SMART-LERECO unit, Rennes, France）；Alain Carpentier（Agricultural Research (INRAE) in the SMART-LERECO unit, Rennes, France）；Fabienne Femenia（Agricultural Research (INRAE) in the SMART-LERECO unit, Rennes, France）

Abstract：Null crop acreages raise pervasive issues when modeling acreage choices with farm data. We revisit these issues and emphasize that null acreage choices arise not only due to binding non‐negativity constraints but also due to crop production fixed costs. Based on this micro‐economic background, we present a micro‐econometric multicrop model that consistently handles null acreage choices and accounts for crop production fixed costs. This multivariate endogenous regime switching model allows for specific crop acreage patterns, such as multiple kinks and jumps in crop acreage responses to economic incentives that are due to changes in produced crop sets. We illustrate the empirical tractability of our modeling framework by estimating a random parameter version of our model on a panel dataset of French farmers. The estimated model is used to simulate the impacts of area‐based subsidies on protein peas, which are implemented by the EU for reducing its dependence on imported protein crops. Our results suggest that this subsidy scheme is effective, essentially by leading farmers to incorporate or to keep protein pea in their crop mix.

keywords：acreage choice;crop choice;endogenous regime switching;random parameter models

Price Dispersion in Farmland Markets: What Is the Role of Asymmetric Information?

Volume 103, Issue 4 

August 2021

作者：Stefan Seifert（Rheinische Friedrich-Wilhelms-Universität Bonn）；Christoph Kahle（A doctoral candidate）；Silke Hüttel（Institute for Food and Resource Economics, University of Bonn）

Abstract：This article investigates the role played by information, search, and bargaining cost in agricultural land markets to explain price dispersion. Based on a hedonic model under incomplete information, we build a two‐tier stochastic frontier. By linking costs of being information deficient to agent characteristics such as degree of professionalism, we identify relative price effects of buyer and seller types related to information deficiency. We compile a comprehensive data set of more than 10,000 transactions in Saxony〢nhalt, Germany, between 2014 and 2017. We find institutional sellers to achieve the lowest losses resulting from information deficiency and sell with mark垥恮hereas other sellers incur losses. This seller group could benefit from investments in professionalism and roughly halve their cost of being information deficient. Tenant buyers can benefit from informational advantages resulting in markdowns with lowest effects in the harvest season. We conclude that Germany's policy makers can do more to support market transparency.

keywords：Farmland markets; hedonic pricing; information deficiency; two‐tier frontier

Agricultural Productivity in Space: an Econometric Assessment Based on Farm‐Level Data

Volume 103, Issue 4 

August 2021

作者：Edoardo Baldoni（Department of Economics and Social Sciences, Università Politecnica delle Marche, Ancona, Italy）；Roberto Esposti（Department of Economics and Social Sciences, Università Politecnica delle Marche, Ancona, Italy）

Abstract：This work aims to investigate scale, scope and nature of spatial dependence of agricultural total factor productivity (TFP) by using farm‐level survey data. TFP is measured using transitive index numbers, and the spatial properties of TFP are assessed within a dynamic spatial panel data model designed to separate production fundamentals from productivity spillovers. Because of the statistical issues that typically affect spatial analyses based on survey data, a Bayesian model selection procedure is used to inspect the spatial properties of TFP at different aggregation levels and to search for the most appropriate spatial scale to conduct the investigation. The application concerns Italian FADN farm‐level data over the period 2008–2015 then aggregated at the NUTS3 level. Results suggest that agricultural productivity spillovers significantly occur though over a limited spatial range. The cumulated effects of the estimated diffusion mechanism are described through a set of spatial indicators and presented graphically.

keywords：Dynamic panel models; multilateral TFP index; farm‐level survey data; productivity spatial dependence; spatial aggregation bias; spatial sampling bias

END

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