1. College of Economics and Management; China Agricultural University; 17 Qinghua East Road Haidian District Beijing 100083 China
2. School of Economic Sciences; Washington State University; Pullman WA 99164-6210
3. JP Morgan Chase; 1111 Polaris Parkway Columbus OH 43240-2031
4. Institute of Development and Agricultural Economics; Leibniz University Hannover; 1 Koenigsworther Platz Hannover 30167 Germany