Department of Agricultural and Resource Economics The University of Tokyo Tokyo 113-8657 Japan;
Department of Agricultural and Resource Economics The University of Tokyo Tokyo 113-8657 Japan;
Organization for Regional and Inter-regional Studies Waseda University Tokyo 169-8050 Japan;
College of Economics and Management China Agricultural University Beijing 100083 P.R.China;
Department of Agricultural and Resource Economics The University of Tokyo Tokyo 113-8657 Japan;