1. University of Hohenheim, Germany; Institute for Employment Research (IAB), Nuremberg; Centre for Economic Policy Research (CEPR), London; CESifo, Munich; Institute of Labor Economics (IZA), Bonn
2. University of Fribourg, Department of Economics, Fribourg, Switzerland; CESifo, Munich; Centre for Research and Analysis of Migration (CReAM), University College London; Institute of Labor Economics (IZA), Bonn
3. swissstaffing, Dübendorf, Switzerland