1. MIT Department of Economics, 40 Ames Street Building E17, Room 201A, Cambridge, MA 02142, and J-PAL (e-mail: )
2. Yale University, P.O. Box 208269, New Haven, CT 06520-8269, IPA, J-PAL, and National Bureau of Economic Research (NBER) (e-mail: )
3. Department of Economics, 314 Rockefeller Hall, Dartmouth College, Hanover, NH 03755-3514, IPA, J-PAL, and NBER (e-mail: )