[1] Univ Calif San Francisco, Med Effectiveness Res Ctr Diverse Populat, Dept Obstet Gynecol & Reprod Sci & Epidemiol & Bi, San Francisco, CA 94143 USA
[2] Univ Calif Davis, Ctr Healthcare Policy & Res, Dept Family & Community Med, Davis, CA 95616 USA
[3] Univ Calif Davis, Ctr Healthcare Policy & Res, Dept Pediat, Davis, CA 95616 USA
[4] Univ Minnesota, Sch Publ Hlth, Div Epidemiol & Community Hlth, Minneapolis, MN 55455 USA
[5] McMaster Univ, Dept Clin Epidemiol & Biostat, Hamilton, ON, Canada
[6] Univ Calif Davis, Dept Econ, Davis, CA 95616 USA
[7] Univ Toronto, Dept Med & Hlth Policy Management & Evaluat, Toronto, ON M5S 1A1, Canada
[8] St Michaels Hosp, Ctr Res Inner City Hlth, Keenan Res Ctr, Li Ka Shing Knowledge Inst, Toronto, ON M5B 1W8, Canada
[9] St Michaels Hosp, Div Gen Internal Med, Toronto, ON M5B 1W8, Canada