1. Department of Management, Department of Economics, and Centre for Economic Performance, London School of Economics, Houghton Street, London, WC2A 2AE, United Kingdom, and CEPR (e-mail: )
2. Banque de France, 46-2401 DGEI-DEMS-SAMIC, 75049 Paris Cedex 01, France, Centre for Economic Performance, and CEPR (e-mail: )
3. Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, CEPR, and NBER (email: )