1. Department of Economics and Woodrow Wilson School, Princeton University, Princeton, NJ 08544, Canadian Institute for Advanced Research, Centre for Economic Policy Research, Institute for the Study of Labor, and National Bureau for Economic Research.
2. Institut d'Economie Industrielle, 21 Allées de Brienne, 31000 Toulouse, France, Groupe de Recherche en Économic Mathématique et Quantitative, Centre d'Enseignement et de Recherche en Analyse Socioéconomique, and Massachusetts Institute of Technology.