1. Department of Health Policy and Management, T.H. Chan School of Public Health, Harvard University, 677 Huntington Avenue, Boston, MA 02115-6028 (email: )
2. Department of Economics, Stanford University, 579 Serra Mall, Stanford, CA 94305-6072 (email: )
3. Department of Economics, MIT, 50 Memorial Drive, Cambridge, MA 02142-1347 (email: )
4. Graduate School of Business, Stanford University, 655 Knight Way, Stanford, CA 94305-7298 (email: )
5. School of Medicine, Stanford University, 616 Serra Street, Stanford, CA 94305-6019 (email: )