1. College of Economics and Management, Huazhong Agricultural University, Wuhan 430070, China
2. Department of Economics and Management, Tarim University, Alar 843300, China
3. Division of Agribusiness and Agricultural Economics, Department of Agricultural and Consumer Sciences, Tarleton State University, P.O. Box T-0040, Stephenville, TX 76402, USA
4. New College, University of North Texas, 1155 Union Circle, Denton, TX 76203, USA