1. Institute of Social Science Survey, Peking University, Room 528, No. 5, Science Building, No. 5 Yiheyuan Road, Beijing 100871, China
2. World Bank, Development Research Group, 1818 H Street, NW Washington, DC 20433 USA
3. Institute of Social Science Survey, Peking University, Room 614, No. 5 Science Building, No. 5 Yiheyuan Road, Beijing 100871, China
4. National School of Development, Peking University, 5 Yiheyuan Road, Beijing 100871, China