Set Of Subgame Perfect Equilibria Research Articles

Search for a moving target in a competitive environment

We consider a discrete-time dynamic search game in which a number of players compete to find an invisible object that is moving according to a time-varying Markov chain. We examine the subgame perfect equilibria of these games. The main result of the paper is that the set of subgame perfect equilibria is exactly the set of greedy strategy profiles, i.e. those strategy profiles in which the players always choose an action that maximizes their probability of immediately finding the object. We discuss various variations and extensions of the model.

Optimality, Equilibrium, and Curb Sets in Decision Problems Without Commitment

The paper considers a class of decision problems with an infinite time horizon that contains Markov decision problems as an important special case. Our interest concerns the case where the decision maker cannot commit himself to his future action choices. We model the decision maker as consisting of multiple selves, where each history of the decision problem corresponds to one self. Each self is assumed to have the same utility function as the decision maker. Our results are twofold: Firstly, we demonstrate that the set of subgame optimal policies coincides with the set of subgame perfect equilibria of the decision problem. Furthermore, the set of subgame optimal policies is contained in the set of optimal policies and the set of optimal policies is contained in the set of Nash equilibria. Secondly, we show that the set of pure subgame optimal policies is the unique minimal curb set of the decision problem. The concept of a subgame optimal policy is therefore robust to the absence of commitment technologies.

An Approximate Subgame-Perfect Equilibrium Computation Technique for Repeated Games

This paper presents a technique for approximating, up to any precision, the set of subgame-perfect equilibria (SPE) in repeated games with discounting. The process starts with a single hypercube approximation of the set of SPE payoff profiles. Then the initial hypercube is gradually partitioned on to a set of smaller adjacent hypercubes, while those hypercubes that cannot contain any SPE point are gradually withdrawn. Whether a given hypercube can contain an equilibrium point is verified by an appropriate mixed integer program. A special attention is paid to the question of extracting players' strategies and their representability in form of finite automata.

Cake Division by Majority Decision

We consider a collective choice process where three players make proposals sequentially on how to divide a given quantity of resources. Afterwards, one of the proposals is chosen by majority decision. If no proposal obtains a majority, a proposal is drawn by lot. We establish the existence of the set of subgame perfect equilibria, using a suitable refinement concept. In any equilibrium, the first agent offers the whole cake to the second proposal-maker, who in turn offers the whole cake back to the first agent. The third agent is then indifferent about dividing the cake between himself and the first or the second agent.

A selling mechanism

For the assignment game, we propose the following selling mechanism: sellers, simultaneously, fix their prices first; then buyers, sequentially, decide which object to buy, if any. The first phase of the game determines the potential prices, while the second phase determines the actual matching. We prove that the set of subgame perfect equilibria in pure strategies in the strong sense of the mechanism coincides with the set of sellers' optimal stable outcomes when buyers use maximal strategies.

Strategic bargaining in the variable threat game

In this paper the alternating offer model with an exogenous risk of breakdown is taken to explicitly model the bargaining process underlying the variable threat game (Nash, Econometrica, 1953). A modified version of the variable threat game without commitment is also analysed within a dynamic context. The limit set of subgame perfect equilibria is characterized in both dynamic versions. The analysis gives rise to different results than in the two standard models. By making additional assumptions the original results can be regained, indicating that these are implicitly present in the standard analysis.

Multistage game models and delay supergames

The order of stages in a multistage game is often interpreted by looking at earlier stages as involving more long term decisions. For the purpose of making this interpretation precise, the notion of a delay supergame of a bounded multistage game is introduced. A multistage game is bounded if the length of play has an upper bound. A delay supergame is played over many periods. Decisions on all stages are made simultaneously, but with different delays until they become effective. The earlier the stage the longer the delay. A subgame perfect equilibrium of a bounded multistage game generates a subgame perfect equilibrium in every one of its delay supergames. This is the first main conclusion of the paper. A subgame perfect equilibrium set is a set of subgame perfect equilibria all of which yield the same payoffs, not only in the game as a whole, but also in each of its subgames. The second xmain conclusion concerns multistage games with a unique subgame perfect equilibrium set and their delay supergames which are bounded in the sense that the number of periods is finite. If a bounded multistage game has a unique subgame perfect equilibrium set, then the same is true for every one of its bounded delay supergames. Finally the descriptive relevance of multistage game models and their subgame perfect equilibria is discussed in the light of the results obtained.

Odd man out: the proposal-making model

The proposal-making model is applied to the class of three-player/three-cake problems. The set of subgame perfect equilibria (SPEs) and the limit set of SPE payoffs as the risk of breakdown vanishes is characterized. The necessary and sufficient condition for uniqueness is derived. The results for the alternating offer model play an important role. The model always admits one stationary SPE and this equilibrium is related to a multilateral Nash solution. The stationary SPE is the coalition-proof SPE and the limit result differs from the result known for the model without risk of breakdown.

Perfect equilibria of a model of n-person noncooperative bargaining

We study the set of subgame perfect equilibria associated with then-person noncooperative bargaining mechanism proposed by Hart and Mas-Colell (1992). Our results pertain to transferable utility games. The set of perfect equilibria depends on the parameter representing the “continuation probability,” ϱ. For general TU games, we characterize the set of payoffs from perfect equilibria for (a) small values of ϱ and (b) large values of ϱ. For symmetric games a complete characterization for all values of ϱ is provided.