This paper revisits the problem of adverse selection in the insurance market of Rothschild and Stiglitz. We propose a simple extension of the game-theoretic structure in Hellwig under which Nash-type strategic interaction between the informed customers and the uninformed fi rms results always in a particular separating equilibrium. The equilibrium allocation is unique and Pareto-efficient in the interim sense subject to incentive-compatibility and individual rationality. In fact, it is the unique neutral optimum in the sense of Myerson.

I formalise a rather stylised insurance market with adverse selection as a standard duopoly. I formally specify demand functions and profits and I prove that a Nash equilibrium in pure strategies exists if and only if the well-known Rothschild-Stiglitz allocation is efficient.

We reexamine the core in the adverse selection insurance economy first studied by Rothschild and Stiglitz (1976). Defining blocking in a way that takes private information into account, the core is sometimes empty. We define the coalition-proof core as the set of allocations which are blocked only by allocations which are themselves blocked by coalition-proof allocations. This definition is closely related to Coalition Proof Nash Equilibrium, introduced by Bernheim, Peleg and Whinston (1987). We prove that the coalition-proof core consists of the Miyazaki allocation-- the Pareto-optimal allocation most preferred by low-risk agents. The coalition-proof core is always nonempty in this economy and has attractive continuity properties. Cross- subsidization can occur in the coalition-proof core.

A concise introduction to the theory of contracts, emphasizing basic tools that allow the reader to understand the main theoretical models; revised and updated throughout for this edition. The theory of contracts grew out of the failure of the general equilibrium model to account for the strategic interactions among agents that arise from informational asymmetries. This popular text, revised and updated throughout for the second edition, serves as a concise and rigorous introduction to the theory of contracts for graduate students and professional economists. The book presents the main models of the theory of contracts, particularly the basic models of adverse selection, signaling, and moral hazard. It emphasizes the methods used to analyze the models, but also includes brief introductions to many of the applications in different fields of economics. The goal is to give readers the tools to understand the basic models and create their own. For the second edition, major changes have been made to chapter 3, on examples and extensions for the adverse selection model, which now includes more thorough discussions of multiprincipals, collusion, and multidimensional adverse selection, and to chapter 5, on moral hazard, with the limited liability model, career concerns, and common agency added to its topics. Two chapters have been completely rewritten: chapter 7, on the theory of incomplete contracts, and chapter 8, on the empirical literature in the theory of contracts. An appendix presents concepts of noncooperative game theory to supplement chapters 4 and 6. Exercises follow chapters 2 through 5. Praise for the previous edition: “The Economics of Contracts offers an excellent introduction to agency models. Written by one of the leading young researchers in contact theory, it is rigorous, clear, concise, and up-to-date. Researchers and students who want to learn about the economics of incentives will want to read this primer.”—Jean Tirole, Institut D'Économie Industrielle, Universite des Sciences Sociales, France “Students will find this a very useful introduction to the ideas of contract theory. Salanié has managed to summarize a large amount of material in a relatively short number of pages in a highly accessible and readable manner.”—Oliver Hart, Professor of Economics, Harvard University