1. Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
2. Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
3. Perelman School of Medicine, University of Pennsylvania, Philadelphia
4. Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia
5. Department of Epidemiology, Brown University School of Public Health, Providence, Rhode Island
6. Department of Medicine, University of California, San Francisco
7. Department of Medicine, Brown University and Rhode Island Public Health Institute, Providence, Rhode Island