John B Williamson1, Lianquan Fang2, Esteban Calvo3. 1. Department of Sociology, Boston College, Chestnut Hill, MA 02467, USA. Electronic address: john.williamson@bc.edu. 2. Institute of Latin American Studies, Chinese Academy of Social Sciences, Beijing, China. Electronic address: fanglq@cass.org.cn. 3. School of Business and Economics, Universidad Diego Portales, Chile; Department of Epidemiology, Columbia University, USA; Robert N. Butler Columbia Aging Center, Columbia University, USA. Electronic address: esteban.calvo@udp.cl.