[1] Department of Agricultural and Resource Economics, Jomo Kenyatta University of Agriculture and Technology (JKUAT), P.O Box 62000-00200, Nairobi, Kenya
[2] German Development Institute/Deutsches Institut für Entwicklungspolitik (DIE), Tulpenfeld 6, Bonn,D-53113, Germany
[3] Ulrike Grote Institut für Umweltökonomik und Welthandel, Institute for Environmental Economics and World Trade, Leibniz Universität Hannover, Koenigsworther Platz 1, Hannover,30167, Germany