CARTEL STABILITY IN A DYNAMIC OLIGOPOLY WITH STICKY PRICES

We study the stability of cartels in a differential game model of oligopoly with sticky prices (Fershtman and Kamien 1987). We show that when firms use closed-loop strategies and the rate of increase of the marginal cost is .small enough., the grand coalition (i.e., when the cartel includes all firms) is stable: it is unprofitable for a .firm to exit the cartel. Moreover, a cartel of 3 firms is stable for any positive rate of increase of the marginal cost: it is not profitable for an insider firm to exit the coalition, nor it is profitable for an outsider firm to join the coalition. When firms use open-loop strategies the grand coalition is never stable; moreover, we show that only a cartel of size 2 can be stable and it is so only when the rate of increase of the marginal cost is large enough.

WINNERS AND LOSERS FROM THE GRADUAL FORMATION OF TRADING BLOCS

Although global free trade is efficient, each country’s benefit from free trade depends on the path that leads to the global free trade agreement. Using a dynamic model of trading bloc formation, we show that when global free trade is reached gradually, the countries that are initially excluded gain less than the rest and may be even made worse-off by the final free trade agreement, compared with the initial state of no trading blocs.

Merger Performance under Uncertain Efficiency Gains

In view of the uncertainty over the ability of merging firms to achieve efficiency gains, we model the post-merger situation as a Cournot oligopoly wherein the outsiders face uncertainty about the merged entity’s final cost. At the Bayesian equilibrium, a bilateral merger is profitable provided that non-merged firms sufficiently believe that the merger will generate large enough efficiency gains, even if ex post none actually materialize. The effects of the merger on market performance are shown to follow similar threshold rules. The findings are broadly consistent with stylized facts, and provide a rationalization for an efficiency consideration in merger policy.Horizontal merger, Bayesian Cournot equilibrium, Efficiency gains, Market performance

Random paths to stability in the roommate problem

This paper studies whether a sequence of myopic blockings leads to a stable matching in the roommate problem. We prove that if a stable matching exists and preferences are strict, then for any unstable matching, there exists a finite sequence of successive myopic blockings leading to a stable matching. This implies that, starting from any unstable matching, the process of allowing a randomly chosen blocking pair to form converges to a stable matching with probability one. This result generalizes those of Roth and Vande Vate (1990) and Chung (2000) under strict preferences

Sharing the surplus in games with externalities within and across issues

We consider environments in which agents can cooperate on multiple issues and externalities are present both within and across issues. We propose a way to extend (Shapley) values that have been put forward to deal with externalities within issues to games where there are externalities within and across issues. We characterize our proposal through axioms that extend the Shapley axioms to our more general environment.externalities, cooperative game theory, Shapley value, linked issues.

Sharing the surplus in games with externalities within and across issues

Financial support from ECO2009-7616, ECO2012-31962, 2014SGR-142, the Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2011-0075), ICREA AcademiaWe consider issue-externality games in which agents can cooperate on multiple issues and externalities are present both within and across issues, that is, the amount a coalition receives in one issue depends on how the players are organized on all the issues. Examples of such games are several Örms competing in multiple markets, and countries negotiating both a trade agreement (through, e.g., WTO) and an environmental agreement (e.g., Kyoto Protocol). We propose a way to extend (Shapley) values for partition function games to issue-externality games. We characterize our proposal through axioms that extend the Shapley axioms to our more general environment. The solution concept that we propose can be applied to many interesting games, including intertemporal situations where players meet sequentially

Sharing the surplus in games with externalities within and across issues

We consider environments in which agents can cooperate on multiple issues and externalities are present both within and across issues. We propose a way to extend (Shapley) values that have been put forward to deal with externalities within issues to games where there are externalities within and across issues. We characterize our proposal through axioms that extend the Shapley axioms to our more general environment

Coalitional stability in strategic situations

In many (social, economic, and political) strategic situations, conflict and cooperations coexist and group (or coalitional) behavior is as important as individual behavior. This dissertation studies several issues in such situations.Chapter 1 provides an overview of the theoretical background and motivates the analysis undertaken.Chapter 2 analyzes strategic situations with diverse coalitional interactions to ascertain the "stable" outcomes that will not be replaced by any rational (hence farsighted) coalition of individuals, and the coalitions that are likely to form. The analysis takes into full account the perfect foresight of rational individuals, which has been overlooked in the literature.Chapter 3 defines "negotiation-proof Nash equilibrium", a notion that applies to environments where players can negotiate openly and directly prior to the play of a noncooperative game. The merit of the notion of negotiation-proof Nash equilibrium is twofold: (1) It resolves the nestedness and myopia embedded in the notion of coalition-proof Nash equilibrium. (2) The negotiation process, which is formalized by a "graph", serves as a natural alternative to the approach that models pre-play communication by an extensive form game.Chapter 4 examines the notion of "renegotiation-proofness" in infinitely repeated games. It is shown that imposing renegotiation in all contingencies creates both conceptual and technical difficulties. A notion of self-enforcing agreements is offered: an agreement is self-enforcing if it is immune to any deviation by any coalition which cannot (confidently) count on renegotiation

A Notion of Consistent Rationalizability - Between Weak and Pearce's Extensive Form Rationalizability

Ben-Porath (1997) characterizes the strategies consistent with common certainty of rationality (CCR) and the origin of a generic game of perfect information. More generally, the notion of "weak extensive form rationalizability" (weak EFR) captures the implications initial CCR in an extensive form game. We go one step further by ascertaining at which additional information sets initial CCR can be maintained "consistently". Our consistency notion has two aspects: we examine whether there is "internal consistency" in assuming CCR at a given collection of information sets by using Battigalli and Siniscalchi's (1999) recent result while we introduce "external consistency" to account for all reachable information sets. For a class of games, including all belief- consistent games [cf. Reny (1993)], we identify a unique collection of information sets and hence a unique set of strategy profiles; moreover, we show that in this case our notion is outcome-equivalent to Pearce's (1984) EFR. But in general out notion is between weak and Pearce's EFR.Rationality, beliefs, extensive games, rationalizability