1. Research Fellow at Nuffield College and Department of Economics, Oxford, United Kingdom, and CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas), Buenos Aires, Argentina, and Affiliate Member, Paris School of Economics, Paris, France.
2. Fellow of Nuffield College, Oxford, and Centennial Professor at the London School of Economics, London, United Kingdom.
3. Professor of Economics at the Paris School of Economics, Paris, France.
4. Professor of Economics, University of California at Berkeley, United States.