The Subjective Approach to General Equilibrium under Imperfect Competition

I would like to thank Guido Cazzavillan and Giulio Codognato for their helpful comments and suggestions. The major developments in general equilibrium under imperfect competition have been elaborated within an "objective" approach, namely the cournotian tradition, pioneered by Gabszewicz and Vial (1972). Only a few contributions have been proposed within the "subjective" approach, initiated by Negishi (1961), although that seems to be more appealing, as it is more general and requires less computational ability from the agents’ perspective. In this paper, we study the main problems of the subjective approach to general equilibrium under imperfect competition, with regard to individual rationality, expectations, and coordination. In particular, we investigate the issues related to the adjustment processes, that have thus far received scarce attention in both the subjective and the objective approach. In such a way we clarify the nature of some fundamental problems concerning individual rationality and coordination. In particular, we show that the basic assumptions underlying the equilibrium notions proposed within the cournotian tradition are essentially different from those that characterize Negishi’s approach and the attempts to interpret this author’s theory as a special case of a more general cournotian-type framework (Gary-Bobo (1987), (1989)) are in fact incoherent with the original model. Therefore, we demonstrate that to formalize adjustment mechanisms towards equilibrium within Negishi’s approach raises quite peculiar difficulties, that can be to some extent overcome within the cournotian approach. The main implication of our analysis is that, given the current state of the literature, no satisfactory solution has been provided within the subjective tradition to the problem of formulating a general equilibrium concept based on rationality criteria and coordination mechanisms suitable to be applied to the case of market power and strategic interaction. Journal of Economic Literature Classification Number: D.51.