1. Center for Chinese Agricultural Policy, Institute of Geographical Sciences and Natural Resource Research, Chinese Academy of Sciences (CAS), Building 917, Datun Road, Beijing 100101, China.
2. Department of Agricultural and Resource Economics, University of California, 1 Shields Ave., Davis, CA 95616, USA.
3. Department of Agricultural, Food, and Resource Economics, Rutgers University, 55 Dudley Road, New Brunswick, NJ 08901–8520, USA.
4. Associate Professor, Biotechnology Research Institute, Chinese Academy of Agricultural Sciences (CAAS), 12 Zhongguancun Nandajie, Beijing 100081, China.