Unique Implementation in Auctions and in Public Goods Problems

Des conditions nouvelles sont présentées, assurant l’existence de mécanismes d’enchères ou de production de biens publics menant à un équilibre unique ou essentiellement unique, lorsque les préférences des agents sont quasi linéaires. Ces conditions portent exclusivement sur la croyance des agents.We present new conditions that guarantee the existence of mechanism with a unique or essentially unique equilibrium in auction and public goods problems with quasi-linear utility functions. These conditions bear only on the information structures of the agents

Utilitarian Collective Choice and Voting

In his seminal Social Choice and Individual Values, Kenneth Arrow stated that his theory applies to voting. Many voting theorists have been convinced that, on account of Arrow’s theorem, all voting methods must be seriously flawed. Arrow’s theory is strictly ordinal, the cardinal aggregation of preferences being explicitly rejected. In this paper I point out that all voting methods are cardinal and therefore outside the reach of Arrow’s result. Parallel to Arrow’s ordinal approach, there evolved a consistent cardinal theory of collective choice. This theory, most prominently associated with the work of Harsanyi, continued the older utilitarian tradition in a more formal style. The purpose of this paper is to show that various derivations of utilitarian SWFs can also be used to derive utilitarian voting (UV). By this I mean a voting rule that allows the voter to score each alternative in accordance with a given scale. UV-k indicates a scale with k distinct values. The general theory leaves k to be determined on pragmatic grounds. A (1,0) scale gives approval voting. I prefer the scale (1,0,-1) and refer to the resulting voting rule as evaluative voting. A conclusion of the paper is that the defects of conventional voting methods result not from Arrow’s theorem, but rather from restrictions imposed on voters’ expression of their preferences. The analysis is extended to strategic voting, utilizing a novel set of assumptions regarding voter behavior

Competition, coordination and anti-trust policy

In a simple model of horizontal differentiation with free entry (entry occurring in a preliminary stage), it is shown that "tough" price competition, in the Bertrand sense, may be associated to higher industry concentration and lower collective welfare than "soft" price competition in the Cournot sense.Dans un modèle simple de différenciation horizontale avec libre entrée (l'entrée se décidant à une étape préliminaire), on montre qu'une concurrence "forte" au sens de Bertrand peut être associée à structure industrielle plus concentrée et à un bien-être collectif moins élevé qu'une concurrence "raisonnable" au sens de Cournot.d'Aspremont Claude, Motta Massimo. Competition, coordination and anti-trust policy. In: Cahiers d'économie politique, n°37, 2000. Qu'a-t-on appris sur la concurrence imparfaite depuis Cournot? pp. 141-154

Utility theory and ethics

This chapter discusses various technical constructions and philosophical interpretations of utility theory with a view of establishing its relevance to social ethics.