1. Department of Economics, Copenhagen Business School , Porcelænshaven 16A, Frederiksberg DK-2000, Denmark. e-mail: mg.eco@cbs.dk
2. Faculty of Business and Economics, TU Dortmund University , Vogelpothsweg 87, Dortmund D-44221, ZEW Mannheim; IZA Bonn and KU Leuven, Leuven, Belgium. e-mail: Kornelius.Kraft@tu-dortmund.de