1. Population Research Center and Department of Sociology, University of Texas at Austin, 110 Inner Campus Drive Stop G1800, Austin, TX 78712-1699, USA
2. Population Research Center and Department of Sociology, University of Texas at Austin, Austin, TX 78712, USA
3. Harvard Center for Population and Development Studies, Harvard University, Cambridge, MA, USA
4. Institute of Public and International Affairs, University of Utah, Salt Lake City, UT, USA