1. World Bank, 1818 H Street, NW, Washington, DC 20433 (e-mail: )
2. International Food Policy Research Institute, 2033 K Street, NW, Washington, DC 20006 (e-mail: )
3. Department of Agricultural and Consumer Economics, University of Illinois, 326 Mumford Hall, 1301 W. Gregory Drive, Urbana, IL 61801 (e-mail: )