Do Walrasian markets function orderly in the presence of adverse selection? In particular, is their outcome efficient? This paper addresses these questions in the context of a Rothschild and Stiglitz insurance economy. We identify an externality associated with the presence of adverse selection as a special form of consumption externality. Consequently, we show that while competitive equilibria always exist, they are not typically incentive efficient. However, as markets for pollution rights can internalize environmental externalities, markets for consumption rights can be designed so as to internalize the consumption externality due to adverse selection. With such markets competitive equilibria exist and are always incentive efficient. Moreover, any incentive efficient allocation can be decentralized as a competitive equilibrium.

Adverse selection is an important problem in many markets. Governments respond to it with complex regulations: mandates, community rating, subsidies, risk adjustment, and regulation of contract characteristics. This paper proposes a perfectly competitive model of a market with adverse selection. Prices are determined by zero-profit conditions, and the set of traded contracts is determined by free entry. Crucially for applications, contract characteristics are endogenously determined, consumers may have multiple dimensions of private information, and an equilibrium always exists. Equilibrium corresponds to the limit of a differentiated products Bertrand game.We apply the model to show that mandates can increase efficiency but have unintended consequences. An insurance mandate can increase adverse selection on the intensive margin and lead some consumers to purchase less coverage. Optimal regulation addresses adverse selection on both the extensive and the intensive margins, can be described by a sufficient statistics formula, and includes elements that are commonly used in practice.

This book provides a comprehensive introduction to modern auction theory and its important new applications. It is written by a leading economic theorist whose suggestions guided the creation of the new spectrum auction designs. Aimed at graduate students and professionals in economics, the book gives the most up-to-date treatments of both traditional theories of 'optimal auctions' and newer theories of multi-unit auctions and package auctions, and shows by example how these theories are used. The analysis explores the limitations of prominent older designs, such as the Vickrey auction design, and evaluates the practical responses to those limitations. It explores the tension between the traditional theory of auctions with a fixed set of bidders, in which the seller seeks to squeeze as much revenue as possible from the fixed set, and the theory of auctions with endogenous entry, in which bidder profits must be respected to encourage participation.

The first volume of this wide-ranging Handbook contains original contributions by world-class specialists. It provides up-to-date surveys of the main game-theoretic tools commonly used to model industrial organization topics. The Handbook covers numerous subjects in detail including, among others, the tools of lattice programming, supermodular and aggregative games, monopolistic competition, horizontal and vertically differentiated good models, dynamic and Stackelberg games, entry games, evolutionary games with adaptive players, asymmetric information, moral hazard, learning and information sharing models.

The paper analyzes the effects of informational asymmetries on the market structure of the banking industry in a multi-period model of spatial competition. All lenders face uncertainty with regard to borrowers’ creditworthiness, but, in the process of lending, incumbent banks gather proprietary information about their clients, acquiring an advantage over potential entrants. These informational asymmetries are an important determinant of the industry structure and may represent a barrier to entry for new banks. The paper shows that, in contrast with traditional models of horizontal differentiation, the steady-state equilibrium is characterized by a finite number of banks even in the absence of fixed costs.