1. Division of General Internal Medicine, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts
2. Department of Health Care Policy, Harvard Medical School, Boston, Massachusetts3Department of Medicine, Massachusetts General Hospital, Boston4National Bureau of Economic Research, Cambridge, Massachusetts
3. National Bureau of Economic Research, Cambridge, Massachusetts5Department of Ophthalmology, University of Southern California, Los Angeles6Schaeffer Center for Health Policy and Economics, University of Southern California, Los Angeles
4. US Health Resources and Services Administration, Rockville, Maryland