Dr en Droit, Dr en Sciences Economics University Catholique de Louvain, 1963.
Professor of Economics, University Catholique de Louvain, Louvain-laNeuve, Belgium, since 1978. Association Editor, Journal of Economic Theory, 80.
My research interests are mainly centred around the theme of imperfect competition. I was attracted by this topic when writing my doctoral dissertation which dealt with the relationship between the concepts
of core and competitive equilibrium. It was proved by R. V. Aumann (Econometrica, January 1964) that, in atomless exchange economies, the core coincides with the set of competitive allocations.
For years I have studied the nature of the relationship between these two concepts when the exchange economy embodies ‘atoms’ (an atom in a measure space is any subset of positive measure which does not include another subset of positive measure. If this subset is interpreted as coalition of economic agents, it means that this coalition cannot ‘split’. The participants have to act in unison).
Among other results (see Nos. 1 and 3 above), sufficient conditions on the size of cartels have been derived under which Aumann’s result is preserved in spite of the existence of atoms. Another research area in which I have been involved is the extension of the nonco-operative Cournot model to general equilibrium analysis. In my work with J. P. Vial (see No.
4), a general equilibrium model embodying a consumption and a production sector is considered, and a concept of CournotNash equilibrium is derived. More recently, I have been much interested in analysing models with product differentiation ‘à la Hotelling’. Starting from my paper with d’Aspremont and Thisse (No.
7), where it was noticed that the ‘Principle of Minimum Differentiation’ does not hold, I have pursued my work in this area with my colleague, J- F. Thisse. An interesting output of this analysis is the result according to which entry of new firms via differentiated products does not necessarily lead to the competitive outcome: low-quality products are driven out of the market by the entry of higher-quality products, so that only few firms can remain simultaneously in the market (No.