Paolo Bertoletti

Monopolistic Competition when Income Matters

We study monopolistic competition with preferences over differentiated goods characterized by a separable indirect utility rather than a separable direct utility as in the Dixit-Stiglitz model, with the CES case as the only common ground. Examples include linear and log-linear direct demands. In equilibrium with free entry, an increase of the number of consumers is neutral on prices, but increases proportionally the number of firms, just creating pure gains from variety. Contrary to the Dixit-Stiglitz model, an increase in consumer income increases prices and more than proportionally the number of varieties if and only if the price elasticity of demand is increasing. We also discuss extensions to an outside good, heterogeneous consumers, heterogeneous firms a la Melitz and endogenous quality. Finally, we provide an application to international trade generating pricing to market in a generalized Krugman model.

Preferences, entry, and market structure

We provide a unified approach to imperfect (monopolistic, Bertrand, and Cournot) competition when preferences are symmetric over a finite but endogenous number of goods. Markups depend on the Morishima elasticity of substitution and on the number of varieties. The comparative statics of free-entry equilibria is examined, establishing the conditions for markup neutrality with respect to income, market size, and productivity. We compare endogenous and optimal market structures for several non-CES examples. With a generalized linear direct utility, the markup can be constant and optimal under monopolistic competition, and nonmonotonic in the number of firms under Bertrand or Cournot competition.

Welfare effects of discriminatory two-parts tariffs constrained by price caps

Abstract Tariff discrimination by a regulated monopolist is sometimes politically unfeasible on distributional grounds. However, under a simple regulatory constraint, discriminatory two-part tariffs provide a Pareto improvement. This suggests an implementable reform of the uniform tariff used in some public utilities.

A General Theory of Endogenous Market Structures

We provide a unified approach to imperfect (monopolistic, Bertrand and Cournot) competition equilibria with demand functions derived from symmetric preferences over a large but finite number of goods. The equilibrium markups depend on the Morishima Elasticity of Substitution/Complementarity between goods, and can be derived directly from the utility functions and ranked unambiguously. We characterize the endogenous market structures, their dependence on market size, income and firms’ productivity and compare them with the optimal allocations. Finally, we apply our results to the case of preferences such as Generalized Leontief, Generalized linear and Generalized quadratic that we introduce in the literature on imperfect competition.

Monopolistic Competition: A Dual Approach

We study monopolistic competition under indirect additivity of preferences. This is dual to the Dixit-Stiglitz model, where direct additivity is assumed, with the CES case as the only common ground. Other examples include (perceived) demand functions that are exponential or linear. Our equilibrium results are generally in contrast with those received by the literature. An increase of the number of consumers never affects prices and firms’ size, but increases proportionally the number of firms, creating pure gains from variety. An increase in individual income increases prices (and more than proportionally the number of varieties) and reduces firms’ size if and only if the price elasticity of demand is increasing. We also study the endogenous market structure with Bertrand competition (in which a pro-competitive effect of market size arises) and the case for inefficient entry.

Monopolistic Competition, As You Like It

We study imperfect and monopolistic competition with asymmetric preferences over a variety of goods provided by heterogeneous firms. We show how to compute equilibria through the Morishima elasticities of substitution. Simple pricing rules and closed-form solutions emerge under monopolistic competition when demands depend on common aggregators. This is the case for Generalized Additively Separable preferences (encompassing additive preferences and their Gorman-Pollak extensions), implicitly additive preferences and others. For applications to trade, with markups variable across goods of different quality, and to macroeconomics, with markups depending on aggregate variables, we propose specifications of indirectly additive, self-dual addilog and implicit CES preferences.

Debiasing through auction? Inertia in the liberalization of retail markets

We analize a market in the process of liberalization. Consumers are biased in favor of the incumbent firm and we assume that they can discover the true value of new suppliers only by switching. In an infinitely-repeated game setting with Bertrand competition, we first show that efficient entry might not take place. We then evaluate the effect of organizing a public auction for assigning consumers to a default supplier and show that such a mechanism (which respects the freedom of choice by consumers) would support entry efficiency. However, auctioning might also increase inefficient, although temporary, entry.