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409
Rationalizability, learning, and equilibrium in games with strategic complementarities
 ECONOMETRICA  JOURNAL OF THE ECONOMETRIC SOCIETY
, 1990
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Epistemic conditions for Nash equilibrium
, 1991
"... According to conventional wisdom, Nash equilibrium in a game “involves” common knowledge of the payoff functions, of the rationality of the players, and of the strategies played. The basis for this wisdom is explored, and it turns out that considerably weaker conditions suffice. First, note that if ..."
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Cited by 236 (6 self)
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According to conventional wisdom, Nash equilibrium in a game “involves” common knowledge of the payoff functions, of the rationality of the players, and of the strategies played. The basis for this wisdom is explored, and it turns out that considerably weaker conditions suffice. First, note that if each player is rational and knows his own payoff function, and the strategy choices of the players are mutually known, then these choices form a Nash equilibrium. The other two results treat the mixed strategies of a player not as conscious randomization of that player, but as conjectures of the other players about what he will do. When n = 2, mutual knowledge of the payoff functions, of rationality, and of the conjectures yields Nash equilibrium. When n ≥ 3, mutual knowledge of the payoff functions and of rationality, and common knowledge of the conjectures yield Nash equilibrium when there is a common prior. Examples are provided showing these results to be sharp.
An introduction to collective intelligence
 Handbook of Agent technology. AAAI
, 1999
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The Bayesian Foundations of Solution Concepts of Games,” Working
 University of Chicago
, 1986
"... We transform a noncooperative game into a Bayesian decision problem for each player where the uncertainty faced by a player is the strategy choices of the other players, the priors of other players on the choice of other players, the priors over priors, and so on. We provide a complete characterizat ..."
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Cited by 109 (0 self)
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We transform a noncooperative game into a Bayesian decision problem for each player where the uncertainty faced by a player is the strategy choices of the other players, the priors of other players on the choice of other players, the priors over priors, and so on. We provide a complete characterization between the extent of knowledge about the rationality of players and their ability to successively eliminate strategies which are not best responses. This paper therefore provides the informational foundations of iteratively undominated strategies and rationalizable strategic behavior (B.D. Bernheim, Economefrica 52 (1984) 10071028; D. Pearce, Economefrica 52 (1984), 10291050). Sufficient conditions are also found for Nash equilibrium behavior and a result akin to R. J. Aumann (Econometrica 55 (1987) l18) on correlated equilibria, is derived with different hypotheses. Journal of
Intrinsic Robustness of the Price of Anarchy
 STOC'09
, 2009
"... The price of anarchy (POA) is a worstcase measure of the inefficiency of selfish behavior, defined as the ratio of the objective function value of a worst Nash equilibrium of a game and that of an optimal outcome. This measure implicitly assumes that players successfully reach some Nash equilibrium ..."
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Cited by 101 (12 self)
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The price of anarchy (POA) is a worstcase measure of the inefficiency of selfish behavior, defined as the ratio of the objective function value of a worst Nash equilibrium of a game and that of an optimal outcome. This measure implicitly assumes that players successfully reach some Nash equilibrium. This drawback motivates the search for inefficiency bounds that apply more generally to weaker notions of equilibria, such as mixed Nash and correlated equilibria; or to sequences of outcomes generated by natural experimentation strategies, such as successive best responses or simultaneous regretminimization. We prove a general and fundamental connection between the price of anarchy and its seemingly stronger relatives in classes of games with a sum objective. First, we identify a “canonical sufficient condition ” for an upper bound of the POA for pure Nash equilibria, which we call a smoothness argument. Second, we show that every bound derived via a smoothness argument extends automatically, with no quantitative degradation in the bound, to mixed Nash equilibria, correlated equilibria, and the average objective function value of regretminimizing players (or “price of total anarchy”). Smoothness arguments also have automatic implications for the inefficiency of approximate and BayesianNash equilibria and, under mild additional assumptions, for bicriteria bounds and for polynomiallength bestresponse sequences. We also identify classes of games — most notably, congestion games with cost functions restricted to an arbitrary fixed set — that are tight, in the sense that smoothness arguments are guaranteed to produce an optimal worstcase upper bound on the POA, even for the smallest set of interest (pure Nash equilibria). Byproducts of our proof of this result include the first tight bounds on the POA in congestion games with nonpolynomial cost functions, and the first
AllPay contests
 Econometrica
, 2009
"... The copyright to this Article is held by the Econometric Society. It may be downloaded, printed and reproduced only for educational or research purposes, including use in course packs. No downloading or copying may be done for any commercial purpose without the explicit permission of the Econometric ..."
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Cited by 56 (1 self)
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The copyright to this Article is held by the Econometric Society. It may be downloaded, printed and reproduced only for educational or research purposes, including use in course packs. No downloading or copying may be done for any commercial purpose without the explicit permission of the Econometric Society. For such commercial purposes contact the Office of the Econometric Society (contact information may be found at the website http://www.econometricsociety.org or in the back cover of Econometrica). This statement must the included on all copies of this Article that are made available electronically or in any other format. Econometrica, Vol. 77, No. 1 (January, 2009), 71–92
Semiparametric Estimation of a Simultaneous Game with Incomplete Information
 Journal of Econometrics
, 2010
"... We analyze a 2 × 2 simultaneous game. We start by showing that a likelihood function defined over the set of four observable outcomes and all possible variations of the game exists only if players have incomplete information. We assume a general incomplete information structure, where players ’ beli ..."
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Cited by 55 (8 self)
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We analyze a 2 × 2 simultaneous game. We start by showing that a likelihood function defined over the set of four observable outcomes and all possible variations of the game exists only if players have incomplete information. We assume a general incomplete information structure, where players ’ beliefs are conditioned on a vector of signals Z observable by the researcher but whose exact distribution is known only to the players. The resulting BayesianNash equilibrium (BNE) is characterized as a vector of conditional moment restrictions. We show how to exploit the information contained in these equilibrium conditions efficiently. The proposal takes the form of a twostep estimator. The first step estimates the unknown equilibrium beliefs using semiparametric restrictions analog to the population BNE conditions. The second step maximizes a trimmed loglikelihood function using the estimates from the first step as plugins for the unknown equilibrium beliefs. The trimming set is an interior subset of the support of Z where the BNE conditions have a unique solution. The resulting estimator of the vector of structural parameters ‘θ ’ is √ N−consistent and exploits all information in the model efficiently. We allow Z to
Computing Equilibria in MultiPlayer Games
 In Proceedings of the Annual ACMSIAM Symposium on Discrete Algorithms (SODA
, 2004
"... We initiate the systematic study of algorithmic issues involved in finding equilibria (Nash and correlated) in games with a large number of players; such games, in order to be computationally meaningful, must be presented in some succinct, gamespecific way. We develop a general framework for obta ..."
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Cited by 53 (4 self)
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We initiate the systematic study of algorithmic issues involved in finding equilibria (Nash and correlated) in games with a large number of players; such games, in order to be computationally meaningful, must be presented in some succinct, gamespecific way. We develop a general framework for obtaining polynomialtime algorithms for optimizing over correlated equilibria in such settings, and show how it can be applied successfully to symmetric games (for which we actually find an exact polytopal characterization), graphical games, and congestion games, among others. We also present complexity results implying that such algorithms are not possible in certain other such games. Finally, we present a polynomialtime algorithm, based on quantifier elimination, for finding a Nash equilibrium in symmetric games when the number of strategies is relatively small.
Coherent Behavior in Noncooperative Games
 JOURNAL OF ECONOMIC THEORY
, 1990
"... A new concept of mutually expected rationality in noncooperative games is proposed: joint coherence. This is an extension of the “no arbitrage opportunities” axiom that underlies subjective probability theory and a variety of economic models. It sheds light on the controversy over the strategies tha ..."
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Cited by 47 (5 self)
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A new concept of mutually expected rationality in noncooperative games is proposed: joint coherence. This is an extension of the “no arbitrage opportunities” axiom that underlies subjective probability theory and a variety of economic models. It sheds light on the controversy over the strategies that can reasonably be recommended to or expected to arise among Bayesian rational players. Joint coherence is shown to support Aumann’s position in favor of objective correlated equilibrium, although the common prior assumption is weakened and viewed as a theorem rather than an axiom. An elementary proof of the existence of correlated equilibria is given, and relationships with other solution concepts (Nash equilibrium, independent and correlated rationalizability) are also discussed.