1. Education and Human Potential, Federal Institute for Population Research (BiB), Wiesbaden, Germany,
2. School of Business and Economics, Freie Universität Berlin, Berlin, Germany,
3. Confederation of German Employers (BDA), Berlin, Germany,
4. Department of Sociology, Eberhard Karls Universität Tübingen, Wilhelmstrasse 36, Tübingen 72074, Germany,
5. Federal Institute for Population Research (BiB), Wiesbaden, Germany,
6. Max-Planck-Institut für Bildungsforschung, Berlin, Germany,