1. Division of General Internal Medicine and Health Services Research, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
2. Department of Medicine, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California.
3. Departments of Internal Medicine and Pediatrics, University of California, Davis, Davis, California.
4. Rand Corporation, Santa Monica, California.
5. Department of Health Policy and Management, UCLA Fielding School of Public Health, University of California, Los Angeles, California.