1. International Monetary Fund, Washington, DC 20431, Department of Economics, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, England, and Institute for Fiscal Studies, 7 Ridgmount Street, London WC1E 7AE, England.
2. Department of Economics, School of Business and Economics, University of Exeter, Streatham Court, Rennes Drive, Exeter EX4 4PU, England.