1. Collège de France, 3 Rue d’Ulm, 75005 Paris, France, and London School of Economics (email: )
2. Banque de France, 31 Rue Croix des Petits Champs, 75001 Paris, France (email: )
3. Institute for International Economic Studies, Stockholm University, SE-106 91 Stockholm, Sweden (email: )
4. Department of Economics, Stanford University, Stanford, CA 94305 (email: )
5. Federal Reserve Bank of San Francisco, Economics Research, 101 Market Street, San Francisco, CA 94105 (email: )