1. From the Center for Evaluative Clinical Sciences (J.S., A.C.), Dartmouth Medical School, Hanover, NH; Department of Economics (J.S., A.C., D.S.), Dartmouth College, Hanover, NH; National Bureau of Economics Research (J.S., A.C., D.S.), Cambridge, Mass; Congressional Budget Office (J.L.), Washington, DC; and Center for Health Policy and Center for Primary Care and Outcomes Research (M.M.), Stanford University School of Medicine, Palo Alto, Calif.