1. Department of Social Security, School of Labor and Human Resources, Renmin University of China, 59 Zhongguancun Street, Haidian District, Beijing 100872, China
2. Department of Health Policy and Management, Yale School of Public Health, 100 Church Street South, Suite 199, New Haven, CT 06510, USA
3. Global Health Leadership Initiative, Yale University, 100 Church Street South, Suite 199, New Haven, CT 06510, USA