1. Department of Health Care Policy, Harvard Medical School, Boston, Massachusetts2Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts3National Bureau of Economic Research, Cambridge, Massachusetts
2. National Bureau of Economic Research, Cambridge, Massachusetts4Leonard D. Schaeffer Center for Health Policy and Economics, University of Southern California, Los Angeles
3. Leonard D. Schaeffer Center for Health Policy and Economics, University of Southern California, Los Angeles5Department of Emergency Medicine, University of Southern California, Los Angeles