1. Economist, CSIR-Savanna Agricultural Research Institute, P.O. Box TL 52, Tamale, Ghana.
2. Graduate student, Department of Agricultural and Consumer Economics, University of Illinois at Urbana-Champaign, 318 Mumford Hall, 1301 W. Gregory, Urbana, IL 61801, USA.
3. Professor, Department of Agricultural and Consumer Economics, University of Illinois at Urbana-Champaign, 318 Mumford Hall, 1301 W. Gregory, Urbana, IL 61801, USA.