[1] Univ Southern Calif, Leonard D Schaeffer Ctr Hlth Policy & Econ, Los Angeles, CA 90007 USA
[2] Univ Southern Calif, Sol Price Sch Publ Policy, Los Angeles, CA 90007 USA
[3] Univ Southern Calif, Sch Pharm, Dept Pharmaceut & Hlth Econ, Los Angeles, CA USA
[4] Univ Southern Calif, Keck Sch Med, Dept Emergency Med, Los Angeles, CA USA
[5] Univ Calif Los Angeles, David Geffen Sch Med, Dept Emergency Med, Los Angeles, CA 90095 USA
[6] Univ Southern Calif, Keck Sch Med, Dept Prevent Med, Los Angeles, CA USA
[7] Univ Southern Calif, Childrens Hosp Los Angeles, Keck Sch Med, Fetal & Neonatal Inst,Div Neonatol,Dept Pediat, Los Angeles, CA USA