1. Department of Health Policy, The London School of Economics and Political Science, London, Houghton Street, WC2A 2AE, UK
2. Center for Global Development Europe, London, Abbey Gardens, SW1P 3SE, UK
3. Department of Econometrics, Statistics and Applied Economics, Universitat de Barcelona, 08034 Barcelona, Spain
4. Center for Research in Health and Economics, University of Pompeu Fabra, 08005 Barcelona, Spain