1. Alfred-Weber-Institute, University of Heidelberg, Bergheimerstrasse 58, 69115 Heidelberg, Germany.
2. Division of the Humanities and Social Sciences, California Institute of Technology, Mail code 228-77, Pasadena, CA 91125.
3. Institute for Empirical Research in Economics, University of Zürich, Blümlisalpstrasse 10, CH-8006, Zürich, Switzerland.