[1] VATT Inst Econ Res, Arkadiankatu 7, FI-00101 Helsinki, Finland
[2] Univ Warwick, Dept Econ, Gibbet Hill Rd, Coventry CV4 7AL, W Midlands, England
[3] CESIfo, Munich, Germany
[4] Univ Birmingham, Dept Econ, Birmingham B15 2TT, W Midlands, England
[5] CEPR, London, England
[6] London Sch Econ & Polit Sci, Dept Govt, Houghton St, London WC2A 2AE, England