One-dimensional bargaining with a general voting rule

We study a model of multilateral bargaining over social outcomes represented by points in the unit interval. An acceptance or rejection of a proposal is determined by a voting rule as represented by a collection of decisive coalitions. The focus of the paper is on the asymptotic behavior of subgame perfect equilibria in stationary strategies as the discount factor goes to one. We show that, along any sequence of stationary subgame perfect equilibria, as the discount factor goes to one, the social acceptance set collapses to a point. This point, called the bargaining outcome, is independent of the sequence of equilibria and is uniquely determined by the set of players, the utility functions, the recognition probabilities, and the voting rule. The central result of the paper is a characterization of the bargaining outcome as a unique zero of the characteristic equation.microeconomics ;

A General Structure Theorem for the Nash Equilibrium Correspondence

We consider n--person normal form games where the strategy set of each player is a non--empty compact convex subset of a Euclidean space, and the payoff function of player i is continuous in joint strategies and continuously differentiable and concave in player i''s strategy. No further restrictions (such as multilinearity of the payoff functions or the requirement that the strategy sets be polyhedral) are imposed. We demonstrate that the graph of the Nash equilibrium correspondence on this domain is homeomorphic to the space of games. This result generalizes a well--known structure theorem in Kohlberg and Mertens (On the Strategic Stability of Equilibria, Econometrica, 54, 1003--1037, 1986). It is supplemented by an extension analogous to the unknottedness theorems in Demichelis and Germano (On (Un)knots and Dynamics in Games, Games and Economic Behavior, 41, 46--60, 2002): the graph of the Nash equilibrium correspondence is ambient isotopic to a trivial copy of the space of games.mathematical economics;

On the asymptotic uniqueness of bargaining equilibria

The paper studies the model of multilateral bargaining over the alternatives representedby points in the mâdimensional Euclidean space. Proposers are chosen randomly and the acceptance of a proposal requires the unanimous approval of it by all the players. The focus of the paper is on the asymptotic behavior of subgame perfect equilibria in pure stationary strategies (called bargaining equilibria) as the breakdown probability tends to zero. Bargaining equilibria are said to be asymptotically unique if the limit of a sequence of bargaining equilibria as the breakdown probability tends to zero is independent of the choice of the sequence and is uniquely determined by the primitives of the model. We show that the limit of any sequence of bargaining equilibria is a zero point of the soâcalled linearization correspondence. The asymptotic uniqueness of bargaining equilibria is then deduced in each of the following cases: (1) m = n−1, where n is the number of players, (2) m = 1, and (3) in the case where the utility functions are quadratic, for each 1 ≤ m ≤ n−1. In each case the linearization correspondence is shown to have a unique zero. Result 1 hasbeen established earlier in Miyakawa and Laruelle and Valenciano. Result 2 is subsumed by the result in Predtetchinski. Result 3 is new.microeconomics ;

One-dimensional bargaining with unanimity rule

The paper examines bargaining over a one--dimensional set of social states, with a unanimity acceptance rule. We consider a class of delta-equilibria, i.e. subgame perfect equilibria in stationary strategies that are free of coordination failures in the response stage.We show that along any sequence of delta-equilibria, as delta converges to one, the proposal of each player converges to the same limit. The limit, called the bargaining outcome, is uniquely determined by the set of players, the recognition probabilities, and the utility functions, and it is independent of the choice of the sequence. We characterize the bargaining outcome as a unique solution of a characteristic equation.mathematical economics;

The Fuzzy Core and the (Π, β)- Balanced Core

This note provides a new proof of the non-emptiness of the fuzzy core in a pureexchange economy with finitely many agents. The proof is based on the concept of(Π, β)-balanced core for games without side payments due to Bonnisseau and Iehlé(2003).microeconomics ;

On the Non-emptiness of the Fuzzy Core

The seminal contribution of Debreu-Scarf (1963) connects the two concepts of core and competitive equilibrium in exchange economies. In effect, their core-equilibrium equivalence result states that, when the set of economic agents is replicated, the set of core allocations of the replica economy shrinks to the set of competitive allocations. Florenzano (1989) defines the fuzzy core as the set of allocations which cannot be blocked by any coalition with an arbitrary rate of participation and then shows the asymptotic limit of cores of replica economics coincides with the fuzzy core. In this note, we provide an elementary proof of the non-emptiness of the fuzzy core for an exchange economy. Unlike the classical Debreu-Scarf limit theorem and its numerous extensions our result does not require any asymptotic intersection -or limit- of the set of core allocations of replica economies.Fuzzy core, Payoff-dependent balancedness, Exchange economies

On the non-emptiness of the fuzzy core

The seminal contribution of Debreu-Scarf [4] connects the two concepts of core and competitive equilibrium in exchange economies. In effect, their core-equilibrium equivalence result states that, when the set of economic agents is replicated, the set of core allocations of the replica economy shrinks to the set of competitive allocations. Florenzano [6] defines the fuzzy core as the set of allocations which cannot be blocked by any coalition with an arbitrary rate of participation and then shows the asymptotic limit of cores of replica economies coincides with the fuzzy core. In this note, we provide an elementary proof of the non-emptiness of the fuzzy core for an exchange economy. Unlike the classical Debreu-Scarf limit theorem [4] and its numerous extensions our result does not require any asymptotic intersection -or limit- of the set of core allocations of replica economies.Economics ;