[1] UCL, Dept Econ, Gower St, London WC1E 6BT, England
[2] Inst Fiscal Studies, Gower St, London WC1E 6BT, England
[3] Stanford Univ, Dept Econ, 579 Serra Mall, Stanford, CA 94305 USA
[4] Ctr Econ Policy Res, Washington, DC USA
[5] NBER, Cambridge, MA 02138 USA
[6] Tel Aviv Univ, Eitan Berglas Sch Econ, POB 39040, IL-6997801 Tel Aviv, Israel