1. International Center for Higher Education Research, University of Kassel, 34125 Kassel, Germany
2. Economics and Decision Sciences, HEC Paris, 78350 Jouy-en-Josas, France
3. Department of Economics, Ecole Nationale de la Statistique, 91120 Palaiseau, France
4. Department of Economics, École Polytechnique, 91120 Palaiseau, France
5. Development Research Group, World Bank, Washington, DC 20433
6. Faculty of Management, Economics and Social Sciences (WiSo-Faculty), University of Cologne, 50923 Köln, Germany