A Countable Economy: An Example

Weiss (1981) established core equivalence and the existence of competitive equilibria in finitely additive exchange economies. To underline the relevance of finitely additive economies we present in this note an example with a close connection to finite exchange economies.

Price vs. quantity in oligopoly games

Price-setting and quantity-setting oligopoly games lead to extremely dierent outcomes in the market. One natural way to address this problem is to formulate a model in which some rms use price while the remaining rms use quantity as their decision variable. We introduce a mixed oligopoly game of this type and determine its equilibria. In addition, we consider an extension of this mixed oligopoly game through which the choice of the decision variables can be endogenized. We prove the emergence of the Cournot game.

A generalization of correlated equilibrium: A new protocol

A new correlation scheme (leading to a special equilibrium called “soft” correlated equilibrium) is introduced for finite games. After randomization over the outcome space, players have the choice either to follow the recommendation of an umpire blindly or freely choose some other action except the one suggested. This scheme can lead to Pareto-better outcomes than the simple extension introduced by [Moulin, H., Vial, J.-P., 1978. Strategically zero-sum games: the class of games whose completely mixed equilibria cannot be improved upon. International Journal of Game Theory 7, 201–221]. The informational and interpretational aspects of soft correlated equilibria are also discussed in detail. The power of the generalization is illustrated in the prisoners’s dilemma and a congestion game.

Generalized correlated equilibrium for two-person games in extensive form with perfect information

A correlation scheme (leading to a special equilibrium called “soft” correlated equilibrium) is applied for two-person finite games in extensive form with perfect information. Randomization by an umpire takes place over the leaves of the game tree. At every decision point players have the choice either to follow the recommendation of the umpire blindly or freely choose any other action except the one suggested. This scheme can lead to Pareto-improved outcomes of other correlated equilibria. Computational issues of maximizing a linear function over the set of soft correlated equilibria are considered and a linear-time algorithm in terms of the number of edges in the game tree is given for a special procedure called “subgame perfect optimization”.

A vállalati likviditáskezelés szerepe eszközfedezettel rendelkező hitelszerződésekben. Az alkun alapuló megközelítés eredményei (The role of corporate liquidity management under secured debt financing Results of the bargaining approach)

A szerző azt a kérdést vizsgálja, hogy a vállalat működése során a likvid eszközök mekkora arányát tartsa fenn. A kérdést a finanszírozás szemszögéből veti fel, mivel a hitelezés okozta korlátok jelentősen befolyásolják a likvid eszköz tartalékolásának motivációit. A cikk a vállalkozói-hitelezői információs kapcsolat háromféle esetében mutatja be az eszközfedezettel rendelkező hitelek adósságszolgálatát meghatározó tényezőket. Elsőként a teljes információs viszony melletti stratégiákkal meghatározott adósságszolgálatot vizsgálja, majd a második típusú információs kapcsolatban a nem megfigyelhető vállalkozói erőfeszítéseket feltételezve adja meg az adósságszolgálat fizetésének ex ante és ex post egyensúlyát. Harmadikként, a nem igazolható vállalati adatok feltevése mellett teljes és részleges eszközfedezetre is meghatározza az optimális vállalkozói likviditási politikát, és tárgyalja az itt fennálló ellentéteket. Megmutatja, hogy részleges eszközfedezet mellett 1. újratárgyalható a hitelszerződés, és a stratégiai adósságszolgálatot nem lehet elkerülni, 2. a likviditásoptimalizálásnak nincs ex post Pareto-egyensúlyi megoldása, ugyanis a hitelszerződésben részt vevő felek alkuereje határozza meg a vállalat likviditásának szintjét. / === / This paper investigates what the liquid asset ratio for firms should be. Financing constraints significantly influence motivations for liquidity hoarding. The article shows the determinants of secured debt services for three different information cases of a lender-borrower relationship. First, it examines the strategic debt service under full information, and then, assuming non-observable entrepreneurial efforts, it gives the ex ante and ex post equilibria of the strategic debt service. The third case supposes non-verifiable firm information; this provides the optimal corporate liquidity policy and explains the contrary propositions. It shows that under not fully secured collateral, 1. the debt contract is renegotiable; the lender cannot avoid the strategic debt service, 2. there is no ex post optimal Pareto efficient solution to liquidity policy, because the corporate liquidity ratio is determined by the bargaining power of the partners in the debt contract.

Invariance under type morphisms: the bayesian Nash equilibrium

Ely and Peski (2006) and Friedenberg and Meier (2010) provide examples when changing the type space behind a game, taking a "bigger" type space, induces changes of Bayesian Nash Equilibria, in other words, the Bayesian Nash Equilibrium is not invariant under type morphisms. In this paper we introduce the notion of strong type morphism. Strong type morphisms are stronger than ordinary and conditional type morphisms (Ely and Peski, 2006), and we show that Bayesian Nash Equilibria are not invariant under strong type morphisms either. We present our results in a very simple, finite setting, and conclude that there is no chance to get reasonable assumptions for Bayesian Nash Equilibria to be invariant under any kind of reasonable type morphisms.

Non-uniqueness through duality in the von Neumann growth models

Duality can be viewed as the soul of each von Neumann growth model. This is not at all surprising because von Neumann (1955), a mathematical genius, extensively studied quantum mechanics which involves a “dual nature” (electromagnetic waves and discrete corpuscules or light quanta). This may have had some influence on developing his own economic duality concept. The main object of this paper is to restore the spirit of economic duality in the investigations of the multiple von Neumann equilibria. By means of the (ir)reducibility taxonomy in Móczár (1995) the author transforms the primal canonical decomposition given by Bromek (1974) in the von Neumann growth model into the synergistic primal and dual canonical decomposition. This enables us to obtain all the information about the steadily maintainable states of growth sustained by the compatible price-constellations at each distinct expansion factor.

Endogenous Timing of Moves in Bertrand-Edgeworth Triopolies

We determine the endogenous order of moves in which the firms set their prices in the framework of a capacity-constrained Bertrand-Edgeworth triopoly. A three-period timing game that determines the period in which the firms announce their prices precedes the price-setting stage. We show for the non-trivial case (in which the Bertrand-Edgeworth triopoly has only an equilibrium in non-degenerated mixed-strategies) that the firm with the largest capacity sets its price first, while the two other firms set their prices later. Our result extends a finding by Deneckere and Kovenock (1992) from duopolies to triopolies. This extension was made possible by Hirata's (2009) recent advancements on the mixed-strategy equilibria of Bertrand-Edgeworth games.

The prisoners' dilemma, congestion games and correlation

Social dilemmas, in particular the prisoners' dilemma, are represented as congestion games, and within this framework soft correlated equilibria as introduced by Forgó F. (2010, A generalization of correlated equilibrium: A new protocol. Mathematical Social Sciences 60:186-190) is used to improve inferior Nash payoffs that are characteristic of social dilemmas. These games can be extended to several players in different ways preserving some important characteristics of the original 2-person game. In one of the most frequently studied models of the n-person prisoners' dilemma game we measure the performance of the soft correlated equilibrium by the mediation and enforcement values. For general prisoners' dilemma games the mediation value is ∞, the enforcement value is 2. This also holds for the class of separable prisoners’ dilemma games.