Affiliation: | 1. Department of Agricultural &2. Applied Economics , Texas Tech University , Lubbock, TX 79409, USA s.pan@ttu.edu;4. Department of Economics , Iowa State University , Ames, IA 50011, USA;5. Department of Statistics , Iowa State University , Ames, IA 50011, USA;6. Applied Economics , Texas Tech University , Lubbock, TX 79409, USA |