An axiomatization of the egalitarian solutions

The egalitarian solutions for general cooperative games which were defined and axiomatized by Kalai and Samet, are compared to the Harsanyi solution. It is shown that axioms used by Hart to characterize the Harsanyi solution can be used to characterize the (symmetric) egalitarian solution. The only changes needed are the omission of the scale covariance axiom and the inclusion, in the domain of the solution, of games which lack a certain smoothness requirement.     

A remark on the Harsanyi-Selten theory of equilibrium selection

We consider a class of 3-person games in normal form with two pure strategies for each player and two strict equilibrium points. To select one of these two strict equilibrium points as the solution, the equilibrium selection theory of Harsanyi and Selten is applied. The games are constructed in such a way that the a priori probabilities reflect somewhat poorly the risk situation of the players. It is argued and illustrated by examples that this might yield unreasonable results. The a priori probabilities would describe the risk situation of the players more completely if their definition were not based on the expectation of correlated decision behavior.     

多重均衡选择中的风险占优与混合策略

均衡选择理论是博弈理论的重要组成部分.风险占优均衡是人们经济决策或行为的一个主要结果.利用混合策略及其性质和“抵制”的概念,“支持”了海萨尼和泽尔腾用公理定义的风险占优概念,且具体给出了识别风险占优均衡的标准和方法,并把它们推广到对称博弈中去.最后对均衡占优的直觉概念和风险占优相冲突的一些博弈进行了类似的讨论.     

Harsanyi power solutions for graph-restricted games

We consider cooperative transferable utility games, or simply TU-games, with limited communication structure in which players can cooperate if and only if they are connected in the communication graph. Solutions for such graph games can be obtained by applying standard solutions to a modified or restricted game that takes account of the cooperation restrictions. We discuss Harsanyi solutions which distribute dividends such that the dividend shares of players in a coalition are based on power measures for nodes in corresponding communication graphs. We provide axiomatic characterizations of the Harsanyi power solutions on the class of cycle-free graph games and on the class of all graph games. Special attention is given to the Harsanyi degree solution which equals the Shapley value on the class of complete graph games and equals the position value on the class of cycle-free graph games. The Myerson value is the Harsanyi power solution that is based on the equal power measure. Finally, various applications are discussed.     

Consistency and the graph Banzhaf value for communication graph games

The graph Banzhaf value was introduced and axiomatically characterized by Alonso-Meijide and Fiestras-Janeiro (2006). In this paper we propose the reduced game and consistency of the graph Banzhaf value for communication situations. By establishing the relationship between the Harsanyi dividends of a coalition in a communication situation and the reduced communication situation, we provide a new axiomatization of the graph Banzhaf value by means of the axioms of consistency and standardness.     

Absorbing set forn-person games

This study tries to modify von Neumann and Morgenstern (vN-M) solution. As with John Harsanyi in 1974, vN-M solution is viewed in a dynamic sense. The final outcome of a game not only depends on the ability of players and standards of behavior of the particular society but also upon which imputation is proposed first. An absorbing property is obtained as a result of modifying the bargaining process of Harsanyi. This modified solution concept maintains the internal stability condition of vN-M solution, and replaces their external stability condition by this absorbing property.

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Zusammenfassung Diese Arbeit zielt auf eine Modifizierung des Begriffs der von Neumann-Morgenstern (vN-M) Lösung. In Anlehnung an John Harsanyi (1974) werden vN-M-Lösungen dynamisch interpretiert. Das endgültige Ergebnis eines Spiels hängt nicht nur von der Fähigkeit der Spieler und den Verhaltensstandards einer bestimmten Gesellschaft ab, sondern auch davon, welche Imputation zunächst vorgeschlagen wird. Durch eine entsprechende Modifizierung des von Harsanyi vorgeschlagenen Verhandlungsprozesses erhält man eine Absorbtionseigenschaft. Das demgemäß modifizierte Lösungskonzept erhält die interne Stabilitätsbedingung der vN-M-Lösung und ersetzt die externe Stabilitätsbedingung durch die Absorbtionseigenschaft.

     

Equilibrium selection in a bargaining problem with transaction costs

It is the purpose of the paper to analyse a bargeining situation with the help of the equilibrium selection theory of John C. Harsanyi and Reinhard Selten. This theory selects one equilibrium point in every finite non-cooperative game. The bargaining problem is the following one: the two bargainers — player 1 and player 2 — simultaneously and independently propose a payoffx of player 1 in the interval 〈0, 1〉. If agreement is reached player 2's payoffs is 1?x. Otherwise both receive zero. Each playeri has a further alternativeW _i , namely not to bargain at all (i=1, 2). Thereby he avoids transaction costsc andd of bargaining which arise whether an agreement is reached or not. One may think of an illegal deal where bargaining involves a risk of being punished — independently whether the deal is made or not. The model has the form of a (K+1)×(K+1)-bimatrix game. It is assumed that there is an indivisable smallest money unit. The game hasK+1 pure strategy equilibrium points.K of them correspond to an agreement and the last one is the strategy pair where both players refuse to bargain. Each of theK+1 equilibrium points can be the solution of the game. The aim of the Harsanyi-Selten-theory is to select in a unique way one of these equilibrium points by an iterative process of elimination (by payoff dominance and risk dominance relationships) and substitution. For each parameter combination (c, d) a sequence of candidate sets arises which becomes smaller and smaller until finally a candidate set with exactly one equilibrium point — the solution of the game — is found. For the sake of shortness the paper will report results without detailed proofs, which can be found elsewhere [Leopold-Wildburger].     

Value theory without symmetry

We investigate quasi-values of finite games – solution concepts that satisfy the axioms of Shapley (1953) with the possible exception of symmetry.  Following Owen (1972), we define “random arrival', or path, values: players are assumed to “enter' the game randomly, according to independently distributed arrival times, between 0 and 1; the payoff of a player is his expected marginal contribution to the set of players that have arrived before him.  The main result of the paper characterizes quasi-values, symmetric with respect to some coalition structure with infinite elements (types), as random path values, with identically distributed random arrival times for all players of the same type.  General quasi-values are shown to be the random order values (as in Weber (1988) for a finite universe of players).  Pseudo-values (non-symmetric generalization of semivalues) are also characterized, under different assumptions of symmetry. Received: April 1998/Revised version: February 2000     

On the difficulty of extending the coco value to games with more than two players

Kalai and Kalai (2013) presented five axioms for solutions of 2-person semi-cooperative games: games in which the basic data specifies individual strategies and payoffs, but in which the players can sign binding contracts and make utility transfers. The axioms pin down a unique solution, the coco value. I show that if one adds a mild dummy player axiom to the list, then the axioms become inconsistent when there are more than two players.     

On non-transferable utility games with coalition structure

We introduce a solution function for Non-transferable Utility (NTU) games when prior coalition structure is given. This solution function generalizes both the Harsanyi solution function forNTU games and the Owen solution forTU games with coalition structure.I would like to thank Sergiu Hart, Bezalel Peleg and Shmuel Zamir for some conversations and constructive remarks on an earlier version of this paper. Part of this research was supported by the Sonderforschungsbereich 303 in the university of Bonn.