1. aDepartment of Demography, University of California at Berkeley, Berkeley, CA, United States of America (USA).
2. bDepartment of Health Statistics and Informatics, World Health Organization, Geneva, Switzerland.
3. cDepartment of Reproductive Health and Research, World Health Organization, 20 avenue Appia, 1211 Geneva 27, Switzerland.
4. dHuman Development Network, The World Bank, Washington DC, USA.