About the Authors
Department of Society, Human Development and Health, Harvard School of Public Health, Boston, Massachusetts, United States of America
Europe and Central Asia Human Development Sector, The World Bank, Washington, D.C., United States of America
The authors have declared that no competing interests exist.
Conceived and designed the experiments: WMM SVS. Analyzed the data: GH. Contributed reagents/materials/analysis tools: SVS. Wrote the paper: GH WMM SVS.