1. Department of Applied Economics, University of Minnesota, St. Paul, MN 55108
2. Center for Global Trade Analysis, Department of Agricultural Economics, Purdue University, West Lafayette, IN 47907-2056
3. Global Program on Sustainability, The World Bank, Washington DC 20006
4. Independent Consultant, Bristol BS7 8E, United Kingdom
5. Department of Economics, University of Victoria, BC V8P 5C2, Canada