1. Department of Agricultural Economics, Kansas State University, Manhattan, KS 66506, USA.
2. Department of Economics, University of Virginia, Charlottesville, VA 22904, USA.
3. Department of Agricultural, Food, and Resource Economics, Michigan State University, East Lansing, MI 48824, USA.
4. Department of Economics and Center for Agricultural and Rural Development, Iowa State University, Ames, IA 50011, USA.