1 LBJ School of Public Affairs and Population Research Center, The University of Texas at Austin, P.O. Box Y, Austin, TX, 78713, USA. jangel@austin.utexas.edu.
2 Department of Sociology, 3.530 CLA A1700, The University of Texas, Austin, TX, 78712, USA.
3 National Institute of Geriatrics, National Institutes of Health, Blvd. Adolfo Ruiz Cortines No. 2767, Colonia San Jeronimo Lidice, 10200, Mexico City, Mexico.
4 Department of Epidemiology, University of Iowa College of Public Health, Room S422 CPHB, 145 N. Riverside Dr, Iowa City, IA, 52242-2007, USA.