1. Department of Economics, Massachusetts Institute of Technology, 50 Memorial Drive, Cambridge, MA 02139.
2. Sloan School of Management, MIT, 50 Memorial Drive, Cambridge, MA 02139, and International Monetary Fund.
3. Department of Government and IQSS, Harvard University, 1737 Cambridge St., Cambridge MA 02138.
4. Columbia University, Graduate School of Business, Uris Hall, 3022 Broadway, New York, NY 10027.