[1] Stanford Univ, Ctr Poverty & Inequal, Stanford, CA 94305 USA
[2] Stanford Univ, Inst Econ Policy Res, Stanford, CA 94305 USA
[3] Stanford Univ, Ctr Hlth Policy, Stanford, CA 94305 USA
[4] Stanford Univ, Ctr Primary Care & Outcomes Res, Stanford, CA 94305 USA
[5] Stanford Univ, Prevent Res Ctr, Dept Med, Stanford, CA 94305 USA
[6] London Sch Hyg & Trop Med, Dept Publ Hlth & Policy, London WC1, England
[7] Stanford Univ, Dept Med, Div Gen Med Disciplines, Stanford, CA 94305 USA
[8] Univ Toronto, Dalla Lana Sch Publ Hlth, Dept Epidemiol, Toronto, ON, Canada
[9] Univ Toronto, Dept Social & Behav Sci, Dalla Lana Sch Publ Hlth, Toronto, ON, Canada
[10] Univ N Carolina, Dept Hlth Behav, Gillings Sch Global Publ Hlth, Chapel Hill, NC USA
[11] Univ Calif San Francisco, Dept Epidemiol & Biostat, San Francisco, CA 94143 USA
[12] Harvard Univ, Sch Publ Hlth, Dept Social & Behav Sci, 665 Huntington Ave, Boston, MA 02115 USA