1. Department of Economics, Massachusetts Institute of Technology, 50 Memorial Drive, E52-438, Cambridge, MA 02142, and National Bureau of Economic Research (email: )
2. School of Education and Social Policy, Northwestern University, 2120 Campus Drive, Evanston IL 60208, and National Bureau of Economic Research (email: )
3. Department of Economics, Emory University, 1602 Fishburne Drive, Atlanta, GA 30322, and National Bureau of Economic Research (email: )
4. University of Florida, 1701 SW 16th Avenue, Gainesville, FL 32608 (email: )
5. Anderson School of Management, UCLA, 110 Westwood Plaza C521, Los Angeles, CA 90095 (email: )