Incorporating risk in a positive mathematical programming framework: a dual approach

In this study we develop a new methodological proposal to incorporate risk into a farm‐level positive mathematical programming (PMP) model. We estimate simultaneously the farm nonlinear cost function and a farmer‐specific coefficient of absolute risk aversion as well as the resource shadow prices. The model is applied to a sample of representative arable crop farms from the Emilia‐Romagna region in Italy. The estimation results confirm the calibration ability of the model and reveal the values of the individual risk aversion coefficients. We use the model to simulate different scenarios of crop price volatility, in order to explore the potential risk management role of an agri‐environmental scheme.     

Disaggregating the Demand for Pesticides: Does it Matter?

This paper analyzes the demand of French farmers for pesticides by disaggregating among the three main categories of pesticides. We estimate the demand elasticities of herbicides, insecticides, and fungicides with respect to pesticide expenditure, and also consider crop differentiation. We retain a Linear Approximated Almost Ideal Demand System specification. A Full‐Information Maximum Likelihood estimation procedure is used to deal with corner solution problems and censored data. The estimation is based on two cross‐sections covering pesticide use of three major crops cultivated in France in 2001 and 2006. Our results show that farmers' response to price variation is very low, especially for 2001. Furthermore, elasticities of pesticide expenditure are significantly different across categories: the highest levels are obtained for fungicides and the lowest ones for insecticides. Finally, we find higher own‐price elasticities for herbicides and fungicides than for insecticides, which are less frequently used.     

Incomplete Credit Markets and Commodity Marketing Behaviour

We use a simple theoretical model of seasonal market participation in the presence of liquidity constraints and transaction costs to explain the ‘sell low, buy high’ puzzle in which some households do not take advantage of inter‐temporal price arbitrage through storage and sell output postharvest at prices lower than observed prices for purchases in the subsequent lean season. We test our model with data from western Kenya using maximum likelihood estimation of a multivariate sample selection model of market participation. Access to off‐farm income and credit indeed seem to influence crop sales and purchase behaviours in a manner consistent with the hypothesised patterns.     

The welfare cost of Japanese rice policy with home‐good preference and an endogenous import price

The welfare cost of Japanese rice policy is estimated in the context of a large importing country, treating domestically produced rice and imported rice as heterogeneous goods and where there is home‐good preference. Not accounting for this preference will cause the gains from liberalisation to be overestimated. The period that is analysed is 2004–2007, departing from that in previous studies, which do not cover this period of greater deregulation. Rather than use border trade flow data as is customary, we acknowledge the actions of a state trading enterprise and construct and use a unique data set which should better gauge import penetration in the Japanese market for rice. Econometric estimation fails to reject the hypothesis that the Ministry of Agriculture, Forestry and Fisheries prevents imports from affecting the price of domestically produced rice. In the absence of precisely estimated parameter values, simulations of liberalisation are conducted under a range of parameter values and the effects on social welfare calculated. The tariff equivalents of the government's support to rice producers are also estimated with values for the period in excess of 100 per cent.     

Geography of crop yield skewness

Analysis of crop yield distributions provides insights into better understanding how natural resources shape agricultural productivity. This study seeks to provide a rigorous theoretical and empirical understanding of the effects of exogenous geographic and climatic factors on the first three moments of crop yields with focus on the third moment. We hypothesize that exogenous factors having beneficial effects on crop production should make crop yield distributions less positively or more negatively skewed. We employ a large crop insurance data set for corn, soybean, and wheat to find general support for our natural‐resources‐determines‐skewness hypothesis. The proposed statistical method optimally uses correlations between the first three moments. It significantly improves estimation performance over existing methods, including the linear moment model which has been commonly applied in the literature.     

A DYNAMIC PROGRAMMING MODEL OF EARLY POTATO HARVESTING

A vegetable producer often faces complex harvest decisions where yield increases through time and varies across crop area, price is determined in erratic seasonal markets, and harvest rate is constrained. In this paper, a simplified two-period potato harvest problem is developed to define a set of marginal conditions for an optimum. The model is then extended to the multi-period case and numerical solutions are generated for a representative farm in South Wales using dynamic programming. The model provides a general framework for analysing crop harvesting systems and prescribing marginal changes, such as adjustments in the harvest capacity, which improve profitability over myopic harvest patterns.     

Demand for area crop insurance among litchi producers in northern Vietnam

This study examines the need for crop insurance for litchi production in northern Vietnam and how farmers might participate in such a program. Hypothetical insurance programs were developed which proposed all‐risk coverage based on area yields. This coverage was offered to farmers to determine both their interest in the program and how insurance features and farmer characteristics affected their decision to buy insurance. Farmers were also surveyed regarding their production practices, price and yield expectations, and financial and personal characteristics. Even before considering other program costs and government budget constraints, there is not a strong case for establishing a crop insurance program here. Results indicate that while farmer participation would be significant, crop insurance is not needed to achieve policy goals like raising farmer income or guaranteeing subsistence levels of income. Crop insurance is not needed to promote litchi production, which is already expanding rapidly due to its high profitability relative to other farm enterprises. In their choice of coverages, farmers preferred higher yield guarantee levels and lower indemnity prices. Estimated premiums were quite low when expressed as a percent of expected revenue, and farmers were not responsive to changes in premiums. Econometric analysis indicated that high income farmers were more likely to participate, but other farmer characteristics seemed to matter little. Anecdotal evidence suggested that farmers believed the expected area yields used to set insurance coverage levels were too low. Because litchi productivity varies significantly by tree age and the litchi planted area is expanding rapidly, determining appropriate values for expected area yields and insurance coverage levels appeared to be the biggest challenge in program design. It is hypothesized that additional farmer education about the relationship between area and farm yields and other aspects of area insurance could improve such a program's operation. Published by Elsevier Science B.V.     

The potential impact of climate change on Taiwan's agriculture

This paper intends to estimate the potential impact of climate change on Taiwan's agricultural sector. Yield response regression models are used to investigate the climate change's impact on 60 crops. A price‐endogenous mathematical programming model is then used to simulate the welfare impacts of yield changes under various climate change scenarios. Results suggest that both warming and climate variations have a significant but non‐monotonic impact on crop yields. Society as a whole would not suffer from warming, but a precipitation increase may be devastating to farmers.     

Agricultural diversification and integrated pest management in Bangladesh

We study factors associated with a shift toward diversified, high‐valued vegetable crops and the incentives associated with the use of IPM methods for vegetable producers in Bangladesh. The primary objective is to measure how IPM technologies affect the crop and technology choices of low‐income rice farmers. A three‐season household optimisation model is used to study crop and technology choice under price and yield uncertainty. The model is parameterised using data from vegetable farms and experimental IPM trials conducted in Bangladesh. Simulation results show that access to IPM technology and IPM availability combined with access to credit increase household welfare and lead to higher rates of vegetable adoption. Off‐farm employment opportunities work against vegetable cultivation and IPM use by risk‐averse farmers. Implications for policy and extension efforts are highlighted.     

Evaluating the impact of rising fertilizer prices on crop yields

Because of tensions on fossil energy and phosphorus markets, the rise in fertilizer prices observed during the last decades may continue in the future, putting into question production pathways relying heavily on crop intensification. To evaluate how, in this context, economic choices may alter crop yields, we first construct different fertilizer price scenarios to 2050 based on an econometric relation with oil and gas prices. Other possible scenarios, such as the continuation of historical trends, are also considered. The resulting changes in fertilizer price range between +0.8% and +3.6% per year over the 2005–2050 period. These scenarios are tested in a global land‐use model incorporating an endogenous representation of the land–fertilizer substitution. We find that the supply‐side response to rising fertilizer prices could lower crop yields in 2050 from ?6% to ?13%, with a corresponding increase in global cropland area ranging between 100 and 240 Mha if the demand for food and nonfood products has to be met. The sensitivity of these results is tested with regard to assumptions on food consumption, change in potential yield and nutrient use efficiency.     

Shadow pricing diversity in U. S. national forests

Tobit estimation of the market value of timber sales in national forests of North Carolina demonstrates the important effect of stand diversity on the formulation of bid prices for mixed-species timber tracts. The hedonic model generates a shadow price for diversity according to changes in bid prices, an effective shift in the demand curve for auctioned tracts due to stand diversity attributes. This approach contrasts with traditional shadow price analyses that focus on the supply effects of environmental constraints. Results are corrected for the effects of bidder participation, market conditions, production costs, and other stand attributes. Econometric results demonstrate that stand heterogeneity is a highly significant factor influencing the market value of timber sales from national forests of the Appalachian region. Greater heterogeneity results in lower bid prices for timber sales, indicating a positive shadow price for maintenance of stand diversity.     

Spatial Effects within the Agricultural Land Market in Northern Ireland

The importance of dealing properly with spatial effects, such as spatial autocorrelation, in cross‐sectional econometric estimation has become more widely recognised in recent years. Spatial autocorrelation is similar in many ways to serial correlation, but while the latter is ordered on a one‐dimensional time axis, the former is ordered in two dimensions. The multi‐directional nature of spatial dependence means that specialised techniques are needed for diagnostic testing and estimation purposes. This paper uses these specialised diagnostics to test for spatial effects within a hedonic pricing study of the agricultural land market. The tests indicate that spatial autocorrelation (in the form of spatial lag dependence) and spatially distinct sub‐markets (or spatial heterogeneity) are present. Ignoring these effects in the estimation process is likely to lead to biased parameter estimates. Consequently, we re‐specify the hedonic model to allow for these spatial effects. The presence of spatial lag dependence suggests that there is circularity of price setting within the agricultural land market. This means that agricultural land prices are not solely determined by the inherent characteristics of the land, but tend to reflect also the average local price per acre.     

Estimating Input Use and Production Costs From Farm Survey Panel Data

Econometric estimation of enterprise input use and production costs offers a less expensive alternative to special surveys. Estimates of input allocation are of use within programming models, for policy analysis and income forecasting. However, simple ordinary least squares estimation has been plagued by a number of problems and the results have been disappointing. This paper provides some empirical evidence on the extent to which these problems can be overcome, or at least mitigated, through exploitation of panel data sets and appropriate panel data estimation techniques. The results confirm that this approach provides some improvement in estimation results, but some practical and methodological problems remain.     

Interlocked Village Markets and Trader Idiosyncrasy in Rural India

The role of traders and traditional exchange institutions has received little attention in empirical research on rural markets in developing countries. We use detailed data on transactions in a village commodity market in India and identify two observed anomalies: first, the repeal of the law of one price, and second, a trader‐idiosyncratic effect, namely that large volumes are sold to a trader who does not offer the best price. Econometric analysis demonstrates that trader idiosyncrasy can largely be explained by reciprocity motives in interlocked village markets. Reciprocity leads to market inefficiencies and can result in unexpected supply responses.     

Smallholder Supply Response to Marketing Board Activities in a Dual Channel Marketing System: The Case of Zambia

In recent years, parastatal grain marketing boards have re‐emerged as important elements of grain markets in eastern and southern Africa, yet little is known about how farmers are responding to their scaled up activities. This article develops a conceptual model of farmers’ production decisions in the context of dual output marketing channels (government and private sector) when output prices at harvest time and the availability of one of the marketing channels are unknown at planting time. It then applies the model to the case of Zambia and uses nationally representative household‐level panel survey data to estimate the effects of the Food Reserve Agency (FRA), the government parastatal maize marketing board, on smallholder crop production and fallow land. The FRA buys maize from smallholders at a pan‐territorial price that typically exceeds market prices in major maize producing areas. Results suggest that increases in the farmgate FRA maize price raise farmer maize price expectations, which induces a supply response. Smallholders respond to an increase in the FRA price by extensifying their maize production. On average, a 1% increase in the FRA price is associated with 0.06% increases in smallholders’ maize area planted and quantity harvested. There is also some evidence that farmers reduce the area of land under fallow in response to FRA incentives but there is no evidence of reductions in the area planted to other crops.     

Agent‐based modeling for ex ante assessment of tree crop innovations: litchis in northern Thailand

This study uses an agent‐based model for ex ante assessment of agricultural innovations. The model builds on whole farm mathematical programming (MP) and extends the methodology with a spatial representation of the system, the heterogeneity of farm households and landscapes, and the interaction between farm households. We apply the model in a northern Thai watershed to study the potential of four innovations to increase the profitability of litchi orchards. Cost‐benefit analysis shows that each innovation would increase the profitability of litchi growing; however, the results of the agent‐based model show that at current price levels these innovations alone would not be enough to stem the decline in the area under litchis. The model was validated and the sensitivity of the results tested for variations in the irrigated water supply and liquidity. We report on how farmers responded to these results and discuss the implications for other areas in northern Thailand.     

海南省最优森林生态规划研究

在对国内外生态规划研究综述的基础上,通过对海南省最优森林生态规划的研究指出:要使海南省林地、林木和森林环境服务的效益最大,必须调整用材林、防护林、特用林和竹林的面积比例。海南省不同林种林地合理使用的平均影子价格为2512.46元/hm2,特用林的最优估价为4376.04元/hm2。建议,海南省应减少用材林面积的比例,增加防护林面积的比例,围绕生态省的建设,狠抓林种结构调整,使不同林种比例结构适合生态省建设的需要。同时,要注重林业产业结构的调整,使林业生产主要由单一热带作物生产转移到多种林产品生产和服务上来,注重林业优势产业的发展。     

Estimation of Area Elasticities from a Standard Profit Function

This article demonstrates that both crop area and output elasticities can be calculated from a profit function. A Chambers/Just profit function (which includes land allocations as quasi-fixed factors) is used to derive shadow price equations for each crop area allocation. Jointly solving these shadow price equations for crop area makes it possible to calculate individual crop area elasticities. A profit function is specified to represent agricultural producers in the state of Iowa. Shadow price equations are jointly estimated with output supply and input demand equations. From these estimated equations, we derive the individual crop area response and output response to a change in prices.     

Separability in farm-household economics: an experiment with linear programming

The assumption of separability between farm-household production and consumption facilitates analysis, but entails several important restrictions. The implications of assuming separability are discussed here in relation to the modelling of a representative Tongan farm-household. Econometric estimation of household demand is coupled with a linear programming (LP) model of farm-household production. When analysing consumer demand, separable farm-household economics is undoubtedly preferable to ignoring the production/consumption linkages entirely. However, the restrictions which must be imposed on the production side of the separable model are such that a realistic LP solution is unlikely to be obtained. This is likely to be a major deterrent to adopting the separable approach for studies in which the main focus is on production rather than consumption.     

Global food demand,productivity growth,and the scarcity of land and water resources: a spatially explicit mathematical programming approach

In the coming decades, an increasing competition for global land and water resources can be expected, due to rising demand for food and bio‐energy production, biodiversity conservation, and changing production conditions due to climate change. The potential of technological change in agriculture to adapt to these trends is subject to considerable uncertainty. In order to simulate these combined effects in a spatially explicit way, we present a model of agricultural production and its impact on the environment (MAgPIE). MAgPIE is a mathematical programming model covering the most important agricultural crop and livestock production types in 10 economic regions worldwide at a spatial resolution of three by three degrees, i.e., approximately 300 by 300 km at the equator. It takes regional economic conditions as well as spatially explicit data on potential crop yields and land and water constraints into account and derives specific land‐use patterns for each grid cell. Shadow prices for binding constraints can be used to valuate resources for which in many places no markets exist, especially irrigation water. In this article, we describe the model structure and validation. We apply the model to possible future scenarios up to 2055 and derive required rates of technological change (i.e., yield increase) in agricultural production in order to meet future food demand.