Credible assignments can improve efficiency in laboratory public goods games

This paper reports an experiment investigating how assignments improve economic efficiency in a modified version of the standard voluntary-contributions mechanism. The experiment uses a non-binding message that makes common information assignments in the repeated game. A credible assignment is one actually followed by the participants. It turns out to be difficult to credibly assign the symmetric efficient outcome in four person cohorts, but we did discover one assignment that was credible in the last match of the evolutionary repeated game.     

Dynamic coordination games

Summary Gains from coordination provide incentives for delay. In this paper, the extent of delay is studied in a dynamic,N-person, coordination game. There is no social gain from delay, so an equilibrium with delay is always inefficient. For fixedN, there is no coordination failure when the period length is short: all equilibrium outcomes converge to the Pareto efficient outcome as the period length converges to zero. On the other hand, holding period length fixed, there exist equilibria in which delay is proportional toN, for arbitrarily large values ofN. In addition, it can be shown that the possibility of delay depends on the timing of strategic complementarities. However, under certain conditions, delay is shown to be a robust phenomenon, in the sense that well-behaved equilibria exhibit infinite delay forN sufficiently large.This paper grew out of discussions with Christophe Chamley. While writing it I benefited from discussions with Ken Binmore, Russell Cooper, Bob Rosenthal and Michael Manove. Joe Farrell, Drew Fudenberg, Martin Hellwig and Sawoong Kang made very useful comments on an earlier version that led to substantial improvements. Helpful comments were also made by seminar participants at the London School of Economics, the SUNY at Stoney Brook, the NBER Summer Institute, Northwestern University, and the University of Chicago. I would like to thank Nick Yannelis and an anonymous referee for their editorial advice. Financial support for this research was provided by the National Science Foundation under Grant No. SES 9196061.     

Behavioral spillovers in coordination games

Motivated by problems of coordination failure observed in weak-link games, we experimentally investigate behavioral spillovers for minimum- and median-effort coordination games. Subjects play these coordination games simultaneously and sequentially. The results show that successful coordination on the Pareto optimal equilibrium in the median game influences behavior in the minimum game when the games are played sequentially. Moreover, this positive, Pareto-improving spillover is present even when group composition changes across games, although the effect is not as strong. We also find that the precedent for uncooperative behavior in the minimum game does not influence play in the median game. These findings suggest guidelines for increasing cooperative behavior within organizations.     

Evidence on learning in coordination games

This paper reports an experiment designed to detect the influence of strategic uncertainty on behavior in order statistic coordination games, which arise when a player’s best response is an order statistic of the cohort’s action combination. Unlike previous experiments using order statistic coordination games, the new experiment holds the payoff function constant and only changes cohort size and order statistic.

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Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. Related research available at     

Stochastic strategy adjustment in coordination games

Summary. The paper explores a model of equilibrium selection in coordination games, where agents from an infinite population stochastically adjust their strategies to changes in their local environment. Instead of playing perturbed best-response, it is assumed that agents follow a rule of ‘switching to better strategies with higher probability’. This behavioral rule is related to bounded-rationality models of Rosenthal (1989) and Schlag (1998). Moreover, agents stay with their strategy in case they successfully coordinate with their local neighbors. Our main results show that both strict Nash equilibria of the coordination game correspond to invariant distributions of the process, hence evolution of play is not ergodic but instead depends on initial conditions. However, coordination on the risk-dominant equilibrium occurs with probability one whenever the initial fraction contains infinitely many agents, independent of the spatial distribution of these agents. Received: March 14, 2000; revised version: June 21, 2001     

Learning and sophistication in coordination games

This paper studies the role of strategic teaching in coordination games and whether changing the incentives of players to teach leads to more efficient coordination. We ran experiments where subjects played one of four coordination games in constant pairings, where the incentives to teach were varied along two dimensions—the short run cost of teaching and the long run benefit to teaching. We show which aspects of the game lead subjects to adopt long run teaching strategies, and show that subjects try to manipulate their opponent’s actions to pull them out of a situation of coordination failure. We also show that extending a model of decision making by introducing a forward-looking component helps to track teachers’ behaviour more accurately, and describes the way players behave in a more unified way across both teachers and learners.     

Voluntary redistribution mechanism in asymmetric coordination games

Experimental Economics - An inequality game is an asymmetric 2 × 2 coordination game in which player 1 earns a substantially higher payoff than player 2 except in the inefficient Nash...     

Competition and coordination in experimental minority games

This work presents experimental results on a coordination game in which agents must repeatedly choose between two sides, and a positive fixed payoff is assigned only to agents who pick the minoritarian side. We conduct laboratory experiments in which stationary groups of five players play the game for 100 periods, and manipulate two treatment variables: the amount of information about other players’ past choices and the salience of information regarding the game history (i.e., the length of the string of past outcomes that players can see on the screen while choosing). Our main findings can be summarized as follows: aggregate efficiency in the game is in most cases significantly higher than the level corresponding to the symmetric mixed strategy Nash equilibrium. In addition, providing players with information about individual choices in the group does not improve aggregate efficiency with respect to when such information is absent. Displaying information about more rounds than just the previous one, on the other hand, seems to have a positive effect on aggregate efficiency. At the individual level, we find a stronger statistical relation between players’ current choices and their own past choices than between players’ choices and previous aggregate outcomes. In addition, the depth of the relation between present and past choices seems to be affected by the prompt availability of information about the game history. Finally, we detect evidence of a mutual co-adaptation between players’ choices over time that is partly responsible for the high level of efficiency observed.      

Decomposing coordination failure in stag hunt games

Experimental Economics - Many situations involve trading-off what is safe for the individual and what is beneficial for the group. This tension is extensively studied as the “Stag Hunt”...     

Equilibrium selection in coordination games with simultaneous play

Summary. We apply the dynamic stochastic framework proposed in recent evolutionary literature to a class of coordination games played simultaneously by the entire population. In these games payoffs, and hence best replies, are determined by a summary statistic of the population strategy profile. We demonstrate that with simultaneous play, the equilibrium selection depends crucially on how best responses to the summary statistic remain piece-wise constant. In fact, all the strict Nash equilibria in the underlying stage game can be made stochastically stable depending on how the best response mapping generates piece-wise constant best responses. Received: February 12, 2001; revised version: October 29, 2001     

Asymmetric and endogenous within-group communication in competitive coordination games

Within-group communication in competitive coordination games has been shown to increase competition between groups and lower efficiency. This study further explores potentially harmful effects of communication, by addressing the questions of (1) asymmetric communication and (2) the endogenous emergence of communication. Our theoretical analysis provides testable hypotheses regarding the effect of communication on competitive behavior and efficiency. We test these predictions using a laboratory experiment. The experiment shows that although asymmetric communication is not as harmful as symmetric communication, it leads to more aggressive competition and lower efficiency relative to the case when neither group can communicate. Moreover, groups vote to endogenously establish communication channels even though they would earn higher payoffs if jointly they chose to restrict within-group communication.     

On the formation of interaction networks in social coordination games

There are many situations where two interacting individuals can benefit from coordinating their actions. We examine the endogenous choice of partners in such social coordination games and the implications for resulting play. We model the interaction pattern as a network where individuals periodically have the discretion to add or sever links to other players. With such endogenous interaction patterns we see multiple stochastically stable states of play, including some that involve play of equilibria in the coordination game that are neither efficient nor risk-dominant. Thus the endogenous network structure not only has implications for the interaction pattern that emerges, but it also has a significant impact on the play in the coordination game relative to what would arise if the same interaction network were exogenous.     

Social learning in coordination games: does status matter?

We report the results of experiments designed to test the impact of social status on learning in a coordination game. In the experiment, all subjects observe the play of an agent who either has high status or low status. In one treatment the agent is another player in the game; in the other the agent is a simulated player. Status is assigned within the experiment based on answers to a trivia quiz. The coordination game has two equilibria: one is payoff-dominant but risky, and the other is risk-dominant. The latter is most commonly chosen in experiments where there is no coordination device. We find that a commonly observed agent enhances coordination on the payoff-dominant equilibrium more often when the agent has high status.      

Credible delegation

We show that the vertical delegation of decision-making authority to agent firms can act as a credible strategic commitment even when contracts are unobservable (or renegotiable) if and only if multilateral delegation is combined with decentralized ownership of the agent firms. In this case, the possibility of renegotiation of other agents’ contracts constrains the set of contracts acceptable to each agent. Delegation may induce more or less aggressive behavior, depending on the nature of within-structure competition among the agent firms. Thus, delegation may be a valuable, credible strategic commitment mechanism when strategies are either substitutes or complements.     

Equilibrium selection through incomplete information in coordination games: an experimental study

We perform an experiment on a pure coordination game with uncertainty about the payoffs. Our game is closely related to models that have been used in many macroeconomic and financial applications to solve problems of equilibrium indeterminacy. In our experiment, each subject receives a noisy signal about the true payoffs. This game (inspired by the “global” games of Carlsson and van Damme, Econometrica, 61, 989–1018, 1993) has a unique strategy profile that survives the iterative deletion of strictly dominated strategies (thus a unique Nash equilibrium). The equilibrium outcome coincides, on average, with the risk-dominant equilibrium outcome of the underlying coordination game. In the baseline game, the behavior of the subjects converges to the theoretical prediction after enough experience has been gained. The data (and the comments) suggest that this behavior can be explained by learning. To test this hypothesis, we use a different game with incomplete information, related to a complete information game where learning and prior experiments suggest a different behavior. Indeed, in the second treatment, the behavior did not converge to equilibrium within 50 periods in some of the sessions. We also run both games under complete information. The results are sufficiently similar between complete and incomplete information to suggest that risk-dominance is also an important part of the explanation.      

An experimental study of coordination and learning in iterated two-market entry games

Summary. Tacit coordination in large groups is studied in an iterated market entry game with complete information and multiple market capacities that are varied randomly from period to period. On each period, each player must decide independently whether to enter any of the markets, and if entering, which of the two markets to enter. Across symmetric and asymmetric markets, we find remarkable coordination on the aggregate level, which is accounted for by the Nash equilibrium, together with considerable individual differences in frequency of entry and decision rules. With experience, the decisions of most players converge to decision rules with cutoff values on the combined market capacity that determine whether or not to enter but not which of the two markets to enter. This latter decision is determined probabilistically by the differential market capacities. The aggregate and individual results are accounted for quite well by a reinforcement-based learning model that combines deterministic and probabilistic elements.     

Credible communication in dynastic government

This paper studies information disclosure in a model of dynastic government. When information about past policy choices comes exclusively from the reports of previous administrations, each administration has an incentive to choose its (suboptimal) one-shot expenditure policy, and then misrepresent its choice to its successor. Consequently, it has been suggested that “horizontal accountability,” i.e., a system of governance where auditing functions lie outside the executive branch, can ensure credible disclosure of a government's activities. This paper suggests a cautious approach to that view.The baseline model examines the reporting incentives of an external auditor who can independently verify the information each period. Even with auditing, credible disclosure is shown to be problematic. Various extensions to this baseline model are examined. In one extension, “liberal” (i.e., those prefering larger government expenditures) and “conservative” (those prefering smaller expenditures) regimes and auditors evolve over time. It is shown that “conservative” (“liberal”) auditors are not credible when the current regime is also “conservative” (“liberal”). Moreover, because information transmission stops when the auditor's and the regime's biases coincide, effective deterrents even in the “good” periods (when the auditor's and the administration's biases differ) are difficult to construct. In all periods the equilibrium requirement of auditor neutrality constrains the dynamic incentives for efficient policy choices. These constraints are shown to bind away from optimal policies in standard constructions of equilibrium. Various ways in which auditing protocols can overcome these problems are discussed.     

Evolutionary selection of ‘chivalrous’ conventions in coordination games without common expectations

We study an evolutionary game-theoretic model where players have to choose within a predetermined set of mixed strategies in a coordination game. Players are of two different kinds, male and female. No common expectations assumption is made; players tend therefore to adopt the strategy that yields larger than average expected payoffs for their kind. In this framework, every stable stationary point of the population dynamics can be interpreted as the emergence of a particular convention. A classification of the possible conventions is provided; conditions for their emergence are determined.     

Credible group stability in many-to-many matching problems

It is known that in two-sided many-to-many matching problems, pairwise-stable matchings may not be immune to group deviations, unlike in many-to-one matching problems (Blair, 1988). In this paper, we show that pairwise stability is equivalent to credible group stability when one side has responsive preferences and the other side has categorywise-responsive preferences. A credibly group-stable matching is immune to any “executable” group deviations with an appropriate definition of executability. Under the same preference restriction, we also show the equivalence between the set of pairwise-stable matchings and the set of matchings generated by coalition-proof Nash equilibria of an appropriately defined strategic-form game.     

Negotiated Enforcement and Credible Deterrence

This paper develops a model of law enforcement in which indicted offenders and the prosecutor can negotiate the penalty prior to the completion of the investigation. The analysis focuses on the credibility of the conviction threat: the prosecutor cannot commit to any predetermined level of investigative effort should the negotiation fail. The settlement stage introduces several new features of the optimal enforcement policy, including the possibility that maximal sanctions may not be optimal. We show that the screening process associated with the negotiation stage reduces the incentives for the prosecutor to undertake thorough investigations and increases the rate of noncompliance.