1. Department of Economics, University of Otago, Dunedin 9054, New Zealand
2. Population Aging Research Center and Department of Sociology, University of Pennsylvania, Philadelphia, PA 19104, USA
3. Department of Economics and Center for International Policy Studies, Fordham University, Bronx, NY 10458, USA
4. Population Studies Center, University of Pennsylvania, PA 19104, USA
5. IZA, Bonn, Germany