1. Department of Economics; Harvard University; Littauer Center 315A, 1805 Cambridge Street Cambridge MA 02138 USA
2. CREI; Ramon Trias Fargas 25-27 08005 Barcelona Spain
3. Universitat Pompeu Fabra; Ramon Trias Fargas 25-27 08005 Barcelona Spain
4. Barcelona GSE; Ramon Trias Fargas 25-27 08005 Barcelona Spain