Een criterium voor het kiezen van een proefopzet

A characterization of D-optimality is given together with several examples where D-optimal designs are computed.     

Rising Food Prices and Household Welfare: Evidence from Brazil in 2008

Food price inflation in Brazil in the 12 months to June 2008 was 18%, whereas overall inflation was 7%. Using spatially disaggregated monthly data on consumer prices and two different household surveys, we estimate the welfare consequences of these food price increases, and their distribution across households. Because Brazil is a large food producer, with a predominantly wage‐earning agricultural labour force, our estimates include general equilibrium effects on market and transfer incomes, as well as the standard estimates of changes in consumer surplus. Although the expenditure (or consumer surplus) effects were large, negative and markedly regressive everywhere, estimates of the market‐income effect were positive and progressive, particularly in rural areas. Because of this effect on the rural poor, and of the partial protection afforded by increases in two large social assistance benefits, the overall impact of higher food prices in Brazil was U‐shaped, with middle‐income groups suffering larger proportional losses than the very poor. Nevertheless, as Brazil is 80% urban, higher food prices still led to a greater incidence and depth of poverty at the national level.     

Guanxi Networks,Buyer-Seller Relationships,and Farmers' Participation in Modern Vegetable Markets in China

The aim of this study is to investigate the joint effects of small-scale farmers’ guanxi networks and buyer-seller relationships on their marketing behavior in China. A survey of 167 vegetable farmers shows that farmers' guanxi networks have significant effect on trusting relationship building with buyers and on their investment behavior for transactional specific assets. Guanxi networks also help to improve farmers’ participation in modern high-value markets (e.g., supermarkets and international markets) and encourage relational transactions. Farmers’ modern market participation will be further enhanced by trusting buyer-seller relationships with buyers and complying with buyers' quality requirements. The application of formal contracts, on the other hand, is closely related to farmers’ trusting relationships with buyers and transactional specific assets for vegetable transactions. Some policy implications are discussed.     

Characterisation and Diagnosis of Rural—Urban Interface Farming in the Tu Liem and Thanh Tri Districts of Hanoi City,Vietnam

A research project was carried out in two areas in the outskirts of Hanoi city using a combination of qualitative and quantitative methods. The objective was to study interactions among the vegetable farming systems and the peri-urban context within which they are situated. The farms studied were characterised as small-scale farms that use high inputs of soil amendments and pesticides for diversified crop rotation systems. The main source of irrigation water and nutrients for vegetable farming in southern Hanoi is wastewater from the To Lich River. In northern Hanoi, irrigation water is obtained directly from the Red River and nutrients are supplied through high fertiliser inputs. The concentrations of COD (144–287 mg l^?1), N-NH₄ ⁺ (1–25 mg l^?1), PO₄ ^3? (0.5–4 mg l^?1) and coliform (525 × 10³?28 × 10⁶ MPN 100 ml^?1) along the To Lich River was much higher than the limits specified in the Vietnamese standard for water used in agriculture. A higher Cu content in soil in Phuc Ly seems to be linked to the high input of chicken manure at the site. However, the contents of heavy metals in irrigation water, in vegetables and in the soil surface layer at the two sites were lower than the Vietnamese maximum permissible levels.     

Analysis of Beef Producers' Risk Management Perceptions and Desire for Further Risk Management Education

Beef cattle producers were surveyed in Texas and Nebraska to investigate perceptions of sources of risk, the effectiveness of risk management strategies, and interest in further risk management education, particularly production risk, using probit analysis. Important decision variables identified are age, prior use of risk management tools, previous attendances of risk management education, and risk aversion. Severe drought and cattle price variability are identified as primary risk factors with potential to affect farm income. Extremely cold weather and disease are of less importance. Understocking pasture and storing hay are perceived most effective as risk management options.     

Willingness to pay for brands: a cross‐region,cross‐category analysis

Using survey data collected in multiple locations (California and Texas in the United States and Revohot in Israel), we quantify category‐ and location‐specific variations of consumers’ willingness to pay (WTP) for brand products after controlling for consumer characteristics. We find that consumers have a similar qualitative assessment of brand value in different product categories across different locations. That is, consumers have a stronger preference and higher WTP for brands in consumer electronics, followed by clothing and then processed food, and the lowest in fresh produce. Furthermore, we simulate price premiums and market shares of brands relative to generic products in different categories. Simulation results suggest that brands in fresh produce have the highest price premium but lowest market share. Despite the similarities, the magnitude of WTP for brands as well as the simulated price premium and the corresponding market share in the same product category are location variant. The similarities and dissimilarities suggest validity of having global brand strategies adapted to local conditions, that is, the so‐called “thinking globally and acting locally” strategy.     

The Costs of Coexistence Measures for Genetically Modified Maize in Germany

We estimate the perceived costs of legal requirements (‘coexistence measures’) for growing genetically modified (GM) Bt maize in Germany using a choice experiment. The costs of the evaluated ex‐ante and ex‐post coexistence measures range from zero to more than €300 per measure and most are greater than the extra revenue the farmers in our survey expect from growing Bt maize or than estimates in the literature. The cost estimates for temporal separation, the highest in our evaluation, imply that the exclusion of this measure in Germany is justified. The costliest measures of the ones that are currently applied in Germany are joint and strict liability for all damages. Our results further show that neighbours do not cause a problem and opportunities for reducing costs through agreements with them exist. Finally, we find that farmers’ attitudes towards GM crops affect the probability of adoption of Bt maize. Our results imply that strict liability will deter the cultivation of Bt maize in Germany unless liability issues can be addressed through other means, for example, through neighbours agreements.