1. Department of Health Policy and Management, School of Public Health, Peking University, Beijing, P. R. China
2. School of Public Administration, Central South University, Changsha, P. R. China
3. Department of Neurology and ICCTR Biostatistics and Research Design Center, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA
4. School of Public Health, Fudan University, Shanghai, P. R. China