Xuan Huo1, Qin Gao2, Fuhua Zhai3, Mingang Lin4. 1. School of Government, Nanjing University, 163 Xianlin Avenue, Nanjing, 210023, China. Electronic address: xhuo@smail.nju.edu.cn. 2. School of Social Work, Columbia University, 1255 Amsterdam Avenue, New York, NY, 10027, USA. Electronic address: qin.gao@columbia.edu. 3. Graduate School of Social Service, Fordham University, 113 West 60(th)Street, New York, NY, 10023, USA. Electronic address: fzhai1@fordham.edu. 4. School of Government, Nanjing University, 163 Xianlin Avenue, Nanjing, 210023, China. Electronic address: mglin@nju.edu.cn.