[1] Inst Fiscal Studies, London, England
[2] UCL, London WC1E 6BT, England
[3] Boston Univ, Boston, MA 02215 USA
[4] CEPR, Washington, DC USA
[5] CREST ENSAE, Malakoff, France
[6] Maastricht Univ, UNU MERIT, Maastricht, Netherlands
[7] NBER, Cambridge, MA 02138 USA
[8] ZEW, Mannheim, Germany
[9] Mannheim Ctr Competit & Innovat, Mannheim, Germany