1. University of Nottingham, School of Economics, Nottingham, NG7 2RD, UK.
2. University of Bonn, Adenauerallee 24, 53113 Bonn, Germany.
3. University of Lausanne, Department of Economics, Internef, 1015 Lausanne, Switzerland.
4. Swarthmore College, Economics Department, 500 College Ave., Swarthmore, PA 19081.