1. Department of Agricultural Economics, Ghent University, Coupure links 653, B-9000 Gent, Belgium
2. Department of Agricultural Economics and Agribusiness Management, College of Agriculture and Veterinary Medicine, Jimma University, Jimma P.O. Box 307, Oromia, Ethiopia
3. Department of Biochemistry and Microbiology, Ghent University, Krijgslaan 281 S2, B-9000 Gent, Belgium