1. Carnegie Mellon University, Heinz College, 5000 Forbes Ave., Pittsburgh, PA 15213-3890, University of Bristol, and National Bureau of Economic Research (NBER).
2. Imperial College, Imperial College Business School, Centre for Health Policy, Level 1–Office 158, Sherfield Building, London, SW7 2AZ, UK.
3. Imperial College, University of Bristol and CEPR, Imperial College Business School, Imperial College London, South Kensington Campus, London SW7 2AZ UK.