1. Department of Economics, University College London, Gower Street, London, WC1E 6BT, United Kingdom, and Institute for Fiscal Studies.
2. Faculty of Economics, University of Cambridge, Sidgwick Avenue, Cambridge CB3 9DD, United Kingdom, and Institute for Fiscal Studies.
3. Departamento de Economía, Universidad de Cantabria, Avda. de los Castros s/n, Santander 39005, Spain, and Fedea.