1. Department of Social Work, The Chinese University of Hong Kong, Hong Kong, China
2. Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY, USA
3. School of Social Policy and Practice, University of Pennsylvania, Philadelphia, PA, USA
4. The Jockey Club Institute of Ageing, The Chinese University of Hong Kong, Hong Kong, China
5. Department of Political Science, Department of Statistics, and School of Education, Iowa State University, Ames, IA, USA