The identification of preferences from equilibrium prices 12 P. - A. Chiappori 3 I. Ekeland 4 F.K¨ ubler 5 H. M. Polemarchakis 6 Discussion Paper No. 99xx (October, 1999) CORE, Universit´ e Catholique de Louvain 1 This text presents results of the Belgian Program on Interuniversity Poles of At- traction initiated by the Belgian State, Prime Minister’s Office, Science Policy Pro- gramming. The scientific responsibility is assumed by its authors. The National Science Foundation provided financial support through the grant SBR 9729559. 2 Donald Brown, G´ erard Debreu, Stefano Demichelis, John Geanakoplos, Fabrizio Germano, Itzhak Gilboa, Roger Guesnerie, Werner Hildenbrand, Rosa Matzkin, Chris Shannon and participants in seminars at the University of Bonn, CentER, the Uni- versity of Chicago, CORE, the Instituto Veneto during the 1999 Summer School in Economic Theory, at Purdue University during the 1999 NBER conference on General Equilibrium, the University of Paris - I, the University of Tel Aviv and the University of Toulouse made helpful comments. 3 Department of Economics, University of Chicago 4 CEREMADE and Institut de Finance, Universit´ e de Paris - IX, Dauphine 5 Department of Economics, Stanford University 6 CORE, Universit´ e Catholique de Louvain