1. Department of Economics and SIPA, Columbia University, International Affairs Building, MC 3308, 420 West 118th Street, New York, NY 10027, and NBER.
2. Applied Economics Department, Guanghua School of Management and IPER, Peking University, Beijing 100871, China.
3. Department of Economics, MIT, 50 Memorial Drive, E52–359, Cambridge, MA 02142, Brookings Institution, and NBER.
4. Department of Economics, School of Economics and Management, Tsinghua University, Beijing 10084, China.