College of Economics and Management Jilin Agricultural University Changchun 130118 P.R.China;
Ministry of Food and Agriculture Department of Economics Accra 183 Ghana;
College of Economics and Management Jilin Agricultural University Changchun 130118 P.R.China;
College of Resources and Environment Sciences Jilin Agricultural University Changchun 130118 P.R.China;
Ghana Cocoa Board Warehousing and Port Operations Accra 1017 Ghana;