Markov perfect equilibria in industries with complementarities

Summary.   This paper considers the existence and computation of Markov perfect equilibria in games with a “monotone” structure. Specifically, it provides a constructive proof of the existence of Markov perfect equilibria for a class of games in which a) there is a continuum of players, b) each player has the same per period payoff function and c) these per period payoff functions are supermodular in the player's current and past action and have increasing differences in the player's current action and the entire distribution of actions chosen by other players. The Markov perfect equilibria that are analyzed are symmetric, not in the sense that each player adopts the same action in any period, but rather in the sense that each player uses the same policy function. Since agents are typically distributed across many states they will typically take different actions. The formal environment considered has particular application to models of industries (or economies) in which firms face costs of price adjustment. It is in this context that the results are developed. Received: November 9, 1999; revised version: February 10, 2000     

Heterogeneous network games: Conflicting preferences

In many economic situations, a player pursues coordination or anti-coordination with her neighbors on a network, but she also has intrinsic preferences among the available options. We here introduce a model which allows to analyze this issue by means of a simple framework in which players endowed with an idiosyncratic identity interact on a social network through strategic complements or substitutes. We classify the possible types of Nash equilibria under complete information, finding two thresholds for switching action that relate to the two-player setup of the games. This structure of equilibria is considerably reduced when turning to incomplete information, in a setup in which players only know the distribution of the number of neighbors of the network. For high degrees of heterogeneity in the population the equilibria is such that every player can choose her preferred action, whereas if one of the identities is in the minority frustration ensues.     

PRICE AND QUANTITY COMPETITION IN A UNIONISED MIXED DUOPOLY: THE CASES OF SUBSTITUTES AND COMPLEMENTS*

We investigate a differentiated mixed duopoly in which private and public firms can choose to strategically set prices or quantities when unions are present. For the case of a unionised mixed duopoly, there exists a dominant strategy only for the public firm that chooses Bertrand competition irrespective of whether the goods are substitutes or complements; there is no dominant strategy for a private firm. Thus, we show that regardless of the nature of goods, social welfare under Bertrand competition is always determined in equilibrium, wherein Bertrand competition entails higher social welfare than Cournot competition. Moreover, our main results hold irrespective of the nature of goods, with the exception that when a sufficiently large parameter of complements is employed, the ranking of a private firm's profit is not reversed, which is in contrast to the standard findings.     

Informational properties of the Nash solutions of two stochastic nonzero-sum games

Within the framework of stochastic two-person nonzero-sum games, we deal with two commonly used models in engineering and economics—namely, the LQG (Linear-Quadratic-Gaussian) and the duopoly problems. We investigate how variations in information available to either player affect the equilibrium Nash strategies for these two models, whose existence and uniqueness have been proven in the paper. We show that for the LQG model better information for either player results in lower average Nash costs for both players; whereas for the duopoly model better information for one player helps him alone to achieve a higher average Nash profit, and it hurts the other player in the sense that his average Nash profit decreases. We further relate these properties of the Nash solutions for these two games to some of the distinct features of zero-sum games and team problems.     

Renegotiation in repeated games

In repeated games, subgame-perfect equilibria involving threats of punishment may be implausible if punishing one player hurts the other(s). If players can renegotiate after a defection, such a punishment may not be carried out. We explore a solution concept that recognizes this fact, and show that in many games the prospect of renegotiation strictly limits the cooperative outcomes that can be sustained. We characterize those outcomes in general, and in the prisoner's dilemma, Cournot and Bertrand duopolies, and an advertising game in particular.     

Bundling strategy and product differentiation

The existing literature shows that a decrease in the degree of substitutability increases a monopoly’s incentive to bundle. This paper in addition takes into account competition in the second product market and then re-examines how intra-brand and inter-brand product differentiations affect the incentive to bundle. In order to formally examine the above conjectures, this research builds up a two-firm, two-product model in which product 1 (monopoly product) is produced only by the bundling firm and product 2 (competing product) is produced by both firms. The analysis shows that under both Bertrand and Cournot competitions the incentive to bundle does not necessarily increase with the degree of intra-brand differentiation, while it strictly decreases with the degree of inter-brand differentiation. Moreover, under Bertrand competition bundling always decreases consumer surplus, but may increase the competitor’s profit and social surplus. Under Cournot competition bundling always reduces the opponent’s profit and social welfare, but may increase consumer surplus.     

Efficiency results in N player games with imperfect private monitoring

We demonstrate that efficiency is achievable in a certain class of N player repeated games with private, almost perfect monitoring. Our equilibrium requires only one period memory and can be implemented by two state automata. Furthermore, we show that this efficiency result holds with any degree of accuracy of monitoring if private signals are hemiindependent. Whereas most existing research focuses on two player cases or only a special example of N player games, our results are applicable to a wide range of N player games of economic relevance, such as trading goods games and price-setting oligopolies.     

Characterization of the extreme core allocations of the assignment game

A characterization of the extreme core allocations of the assignment game is given in terms of the reduced marginal worth vectors. For each ordering in the player set, a payoff vector is defined where each player receives his or her marginal contribution to a certain reduced game played by his or her predecessors. This set of reduced marginal worth vectors, which for convex games coincide with the usual marginal worth vectors, is proved to be the set of extreme points of the core of the assignment game. Therefore, although assignment games are hardly ever convex, the same characterization of extreme core allocations is valid for convex games.     

Revocable pricing can yield collusive outcomes

Traditional models of Bertrand price competition assume irrevocable price announcements. In contrast, when price changes have zero direct costs but sales are thereby delayed, the collusive monopoly outcome is a subgame perfect outcome and is, moreover, the natural focal equilibrium.     

A Syntactic Approach to Knowledge in Finite Games of Perfect Information

In this paper I present a syntactic approach to modeling the interactive knowledge of rationality in finite games of perfect information. This approach allows for a more transparent interpretation. In particular, we have the intuitive picture of viewing knowledge as the input and decisions as the output of a player’s deliberation. This distinction is blurred in the semantic state-space approach.     

Bertrand competition when firms hold passive ownership stakes in one another

We show that the Bertrand oligopoly model with cost asymmetries may admit multiple Nash equilibria when firms hold passive ownership stakes in each other. The equilibrium price may be as high as the monopoly price of the most efficient firm.     

Second Mover Disadvantages in a Three-Player Stackelberg Game with Private Information

I consider a three-player Stackelberg. game where each player has its private signal concerning stochastic demand. I show that at a perfectly revealing equilibrium, the second mover earns the lowest and the third mover the highest expected profit of the three. I characterize this result by the strategic substitutes or complements relationships among three firms at the equilibrium. Journal of Economic Literature Classification Numbers: C72, D82, and L13.     

Alternating-Offer Bargaining with Two-Sided Incomplete Information

I study alternating-offer bargaining games with two-sided incomplete information about the players' discount rates. For both perfect Bayesian equilibrium and a rationalizability-style notion, I characterize the set of expected payoffs which may arise in the game. I also construct bounds on agreements that may be made. The set of expected payoffs is easy to compute and incorporate into applied models. My main result is a full characterization of the set of perfect Bayesian equilibrium payoffs for games in which the distribution over the players' discount rates is of wide support, yet is in a weak sense close to a point mass distribution. I prove a lopsided convergence result: each player cannot gain from a slight chance that she is a strong type, but the player can suffer greatly if there is a slight chance that she is a weak type.     

Infinite horizon common interest games with perfect information

We consider infinite horizon common interest games with perfect information. A game is a K-coordination game if each player can decrease other players' payoffs by at most K times his own cost of punishment. The number K represents the degree of commonality of payoffs among the players. The smaller K is, the more interest the players share. A K-coordination game tapers off if the greatest payoff variation conditional on the first t periods of an efficient history converges to 0 at a rate faster than K^−t as t→∞. We show that every subgame perfect equilibrium outcome is efficient in any tapering-off game with perfect information. Applications include asynchronously repeated games, repeated games of extensive form games, asymptotically finite horizon games, and asymptotically pure coordination games.     

Stochastic games with information lag

Two-player zero-sum stochastic games with finite state and action spaces are known to have undiscounted values. We study such games under the assumption that one or both players observe the actions of their opponent after some time-dependent delay. We develop criteria for the rate of growth of the delay such that a player subject to such an information lag can still guarantee himself in the undiscounted game as much as he could have with perfect monitoring. We also demonstrate that the player in the Big Match with the absorbing action subject to information lags that grows too rapidly will not be able to guarantee as much as he could have in the game with perfect monitoring.     

The value of information in oligopoly with demand uncertainty

This paper discusses the value of information in supermodular and submodular games, using a simple duopoly model where the level of demand is uncertain. It is shown that the value of information issuperadditive (resp.,subadditive) between players if the game issupermodular (resp.,submodular). For example, in a Bertrand (resp., Cournot) market with (possibly imperfect) substitute products, one firm's information acquisition increases (resp., decreases) the other firm's incentive to acquire the same information. Furthermore, when the game is either supermodular or submodular, the value of information is higher when the player isexpected to be informed according to the opponent's belief than when the player is expected to be uninformed; this result is reversed when the game has asymmetric modularity (i.e., one player's action is substitutional to the other's, and the latter's action is complemental to the former's). These qualitative observations have a potential to be applied to a larger class of games with uncertainty where payoffs are smooth (e.g., twice continuously differentiable) in actions and states.     

Learning to play games in extensive form by valuation

Game theoretic models of learning which are based on the strategic form of the game cannot explain learning in games with large extensive form. We study learning in such games by using valuation of moves. A valuation for a player is a numeric assessment of her moves that purports to reflect their desirability. We consider a myopic player, who chooses moves with the highest valuation. Each time the game is played, the player revises her valuation by assigning the payoff obtained in the play to each of the moves she has made. We show for a repeated win-lose game that if the player has a winning strategy in the stage game, there is almost surely a time after which she always wins. When a player has more than two payoffs, a more elaborate learning procedure is required. We consider one that associates with each move the average payoff in the rounds in which this move was made. When all players adopt this learning procedure, with some perturbations, then, with probability 1 there is a time after which strategies that are close to subgame perfect equilibrium are played. A single player who adopts this procedure can guarantee only her individually rational payoff.     

Foreign direct investment,input prices,and host country welfare

This paper analyzes a multinational firm’s foreign direct investment decision, through either greenfield investment or cross‐border merger and acquisition, into a host country with an input monopoly that adopts either uniform pricing or discriminatory pricing. The optimal foreign entry mode could differ under each pricing policy. Under Cournot competition, firms’ technological gap and the initial local market structure are critical to the choice of foreign entry mode, whereas product substitutability is important under Bertrand competition. In the presence of foreign entry, this paper also examines the welfare effects of input price discrimination for the host country.     

Evidence on the equivalence of the strategic and extensive form representation of games

Our experiment tests whether strategically equivalent representations of games produce equivalent behavior when actually played. We examine representative members of the class of generic 2×2 extensive form games of perfect information and the equivalent strategic form games. Systematic differences exist between subjects’ choices in the strategic and extensive form representations. These differences cannot be attributed to differences in subjects’ ability to do backwards induction, in the salience of interpersonal preferences, or in optimization premiums between the two game forms. Instead, subjects in the extensive form are consistently more likely to allow the other player to make a meaningful choice.     

Interactive beliefs,epistemic independence and strong rationalizability

We use a universal, extensive form interactive beliefs system to provide an epistemic characterization of a weak and a strong notion of rationalizability with independent beliefs. The weak solution concept is equivalent to backward induction in generic perfect information games where no player moves more than once in any play. The strong solution concept is related to explicability (Reny,22) and is outcome-equivalent to backward induction in generic games of perfect information.