1. SC Johnson College of Business, Cornell University, Ithaca, New York 14853;
2. National Bureau of Economic Research, Cambridge, Massachusetts 02138;
3. Department of Economics, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong;
4. Guanghua School of Management, Peking University, Beijing 100871, China;
5. Development Strategies and Governance Unit, International Food Policy Research Institute, Washington, District of Columbia 20005