Daniel M Blumenthal1,2, Dana Goldman3,4, Anupam B Jena5,6,7. 1. Cardiology Division, Massachusetts General Hospital, Boston. 2. Harvard Medical School, Boston, Massachusetts. 3. Leonard D. Schaeffer Center for Health Policy and Economics, University of Southern California, Los Angeles. 4. RAND Corporation, Santa Monica, California. 5. Department of Health Care Policy, Harvard Medical School, Boston, Massachusetts. 6. Department of Medicine, Massachusetts General Hospital, Boston. 7. National Bureau of Economic Research, Cambridge, Massachusetts.