[1] Columbia Univ, Dept Econ, New York, NY 10027 USA
[2] Columbia Univ, SIPA, New York, NY 10027 USA
[3] Peking Univ, Guanghua Sch Management, Appl Econ Dept, Beijing 100871, Peoples R China
[4] Peking Univ, IPER, Beijing 100871, Peoples R China
[5] MIT, Dept Econ, Cambridge, MA 02142 USA
[6] Brookings Inst, Washington, DC 20036 USA
[7] NBER, Cambridge, MA 02138 USA
[8] Tsinghua Univ, Dept Econ, Sch Econ & Management, Beijing 10084, Peoples R China