The Origin of the Sylos Postulate: Modigliani's and Sylos Labini's Contributions to Oligopoly Theory

Paolo Sylos Labini's Oligopoly Theory and Technical Progress (1957) is considered one of the major contributions to entry-prevention models, especially after Franco Modigliani's famous formalization. Nonetheless, Modigliani neglected Labini's major aim when reviewing his work (JPE, 1958), particularly his demonstration of the dynamic relation between industrial concentration and economic development. Modigliani addressed only Sylos' microeconomic analysis and the determination of the long-run equilibrium price and output, concentrating on the role played by firms' anticipations. By doing so he shifted attention from Sylos' objective analysis to a subjective approach to oligopoly problem. This paper discusses Sylos' and Modigliani's differing approaches, derives the origin of the Sylos postulate and sets Modigliani's interpretation of Sylos' oligopoly theory in the context of his 1950s research into firms' behaviour under uncertainty.