1. Department of Statistics and Sociology, University of Washington, Seattle, WA, USA
2. Department of Statistics, University of Washington, Seattle, WA, USA
3. London School of Hygiene and Tropical Medicine, London, UK
4. MRC/Wits Rural Public Health and Health Transitions Unit, School of Public Health, University of the Witwatersrand, Johannesburg, South Africa
5. Department of Sociology, the Ohio State University, MRC/Wits Rural Public Health and Health Transitions Unit, School of Public Health, University of the Witwatersrand, Johannesburg, South Africa, ALPHA Network, London School of Hygiene and Tropical Medicine, London, UK, and INDEPTH Network, Accra, Ghana