1. RWTH-Aachen University, Templergraben 64, Rm. 513, 52062 Aachen, Germany and CEPR, IFO Institute, and CESifo (e-mail: )
2. Massachusetts Institute of Technology, Department of Economics, 50 Memorial Drive, Building E52, Room 373A, Cambridge, MA 02142-1347 and National Bureau of Economic Research (e-mail:
3. University of Chile, Department of Economics, Diagonal Paraguay 257 Piso 14, Santiago, Chile and National Bureau of Economic Research (e-mail: )