[1] Johns Hopkins Univ, 3100 Wyman Pk Dr, Baltimore, MD 21211 USA
[2] NBER, 1050 Massachusetts Ave, Cambridge, MA 02138 USA
[3] Univ Michigan, Lorch Hall,611 Tappan Ave, Ann Arbor, MI 48109 USA
[4] CEPR, 2nd Floor,33 Great Sutton St, London EC1V 0DX, England
[5] Singapore Management Univ, 90 Stamford Rd, Singapore 178903, Singapore
[6] World Bank, 1818 H St NW, Washington, DC 20433 USA
[7] Univ Andes, Bogota, Colombia
[8] Cra 1 18a 12, Candelaria, Colombia