1. Institute for Global Health and Development Peking University Beijing China
2. China Center for Health Economic Research Peking university Beijing China
3. School of Public Health, the Key Laboratory of Environmental Pollution Monitoring and Disease Control, Ministry of Education Guizhou Medical University Guiyang China
4. Department of Epidemiology Johns Hopkins Bloomberg School of Public Health Baltimore Maryland USA
5. Welch Center for Prevention, Epidemiology and Clinical Research Johns Hopkins University Baltimore Maryland USA
6. National School of Development Peking University Beijing China