1. Center for Population and Development Studies & Center for Family and Gender Studies, Renmin University of China, Beijing 100872, China
2. School of Sociology and Population Studies, Renmin University of China, Beijing 100872, China
3. School of East Asian Studies, University of Sheffield, Sheffield S3 7RA, UK
4. School of Economics & China Institute for Vitalizing Border Areas and Enriching the People (VBEP), Minzu University of China, Beijing 100081, China