1. Royal Holloway, University of London, Egham Hill, Egham, TW20 0EX, UK.
2. CREI, Universitat Pompeu Fabra, and Barcelona GSE, Ramon Trias Fargas, 25-27, 08005-Barcelona, Spain.
3. Harvard University, Economics Department, Littauer Center, 1805 Cambridge Street, Cambridge, MA 02138.