1. Department of Economics and Center for Agricultural and Rural Development, Iowa State University, Ames, Iowa 50011;
2. Division of Bioeconomics, Department of Earth and Environmental Sciences, KU Leuven, Heverlee, B-3001 Belgium;
3. Department of Economics and LICOS Centre for Institutions and Economic Performance, KU Leuven, Leuven, B-3000 Belgium;
4. Center on Food Security and the Environment, Stanford University, Stanford, California 94305