1. Loyola Marymount University, Los Angeles, California 90045;
2. ICREA, Universitat Pompeu Fabra, IPEG, Barcelona GSE, and CEPR, Barcelona, Spain 08002;
3. Brown University, Providence, Rhode Island 02912;
4. National Bureau of Economic Research, Cambridge, Massachusetts 02138;
5. Carnegie Mellon University, Pittsburgh, Pennsylvania 15213