* Professor of Economics, Aix-Marseille School of Economics (AMSE), CNRS and EHESS, 2 rue de la Charité13002 Marseille cedex, France, Telephone: 33-42914836. Fax: 33-42914873. E-Mail: [email protected]. ** Professor of Economics, University of Nantes, France; Professional address: LEMNA Research Center, Nantes School of Economics and Management I.A.E., University of Nantes, Chemin de la ...