1. Department of Health Research and Policy, HRP Redwood Building, Room 110, Stanford University, Stanford, CA 94305-5405, and NBER.
2. Center for Primary Care and Outcomes Research, 117 Encina Commons, Stanford, CA 94305-6019, and NBER.
3. VA Palo Alto Healthcare System, 111C, 3801 Miranda Avenue, Palo Alto, CA 94304, and Stanford University.