Sustainable Reputations with Rating Systems

In a product choice game played between a long lived seller and an infnite sequence of buyers, we assume that buyers cannot observe past signals. To facilitate the analysis of applications such as online auctions (e.g. eBay), online shopping search engines (e.g. BizRate.com) and consumer reports, we assume that a central mechanism observes all past signals, and makes public announcements every period. The set of announcements and the mapping from observed signals to the set of announcements is called a rating system. We show that, absent reputation effects, information censoring cannot improve attainable payoffs. However, if there is an initial probability that the seller is a commitment type that plays a particular strategy every period, then there exists a finite rating system and an equilibrium of the resulting game such that, the expected present discounted payoff of the seller is almost his Stackelberg payoff after every history. This is in contrast to Cripps, Mailath and Samuelson (2004), where it is shown that reputation effects do not last forever in such games if buyers can observe all past signals. We also construct .nite rating systems that increase payoffs of almost all buyers, while decreasing the seller’s payoff.Reputations, Rating Systems, Online Reputation Mechanisms, Disappearing Reputations, Permanent Reputations. JEL Classification Numbers: D82

Manipulation through political endorsements

We study elections with three candidates under plurality voting. A candidate is a Condorcet loser if the majority of the voters place that candidate at the bottom of their preference rankings. We first show that a Condorcet loser might win the election in a three-way race. Next we introduce to the model an endorser who has private information about the true probability distribution of the preferences of the voters. Observable endorsements facilitate coordination among voters who may otherwise split their votes and lead to the victory of the condorcet loser. When the endorser has an ideological bias towards one of the candidates, the coordination impact of endorsements remains unaltered, moreover the endorser successfully manipulates the outcome of the election in favor of his bias, even if his ideological bias is known by the voters. The results are true for any endorsement cost and any magnitude of bias as long as the electorate is large enough.Strategic voting; Condorcet loser; Signalling; Multiple candidates JEL Classification Numbers: D70, D74, D80

Reputation in the Long-Run with Imperfect Monitoring

We study an infinitely repeated game where two players with equal discount factors play a simultaneous-move stage game. Player one monitors the stagegame actions of player two imperfectly, while player two monitors the pure stagegame actions of player one perfectly. Player one’s type is private information and he may be a “commitment type,” drawn from a countable set of commitment types, who is locked into playing a particular strategy. Under a full-support assumption on the monitoring structure, we prove a reputation result for games with locally nonconflicting interests or games with strictly conflicting interests: if there is positive probability that player one is a particular type whose commitment payoff is equal to player one’s highest payoff, consistent with the players’ individual rationality, then a patient player one secures this type’s commitment payoff in any Bayes-Nash equilibrium of the repeated game. In contrast, if the type’s commitment payoff is strictly less than player one’s highest payoff consistent with the players’ individual rationality, then the worst perfect Bayesian equilibrium payoff for a patient player one is equal to his minimax payoff.Repeated Games, Reputation, Equal Discount Factor, Long-run Players,imperfect Observation, Complicated Types, Finite Automaton JEL Classification Numbers: C73, D83

Bargaining and Reputation in Search Markets

In a two-sided search market agents are paired to bargain over a unit surplus. The matching market serves as an endogenous outside option for agents in a bargaining relationship. Behavioral agents are (strategically inflexible) commitment types that demand a constant portion of the unit surplus. The steady state frequency of behavioral types in the market is determined in equilibrium. We show, even if behavioral types are negligible, they substantially effect the terms of trade and efficiency. In an unbalanced market where the entering flow of one side is short, bargaining follows equilibrium play in a bargaining game with one-sided reputation, the terms of trade are determined by the commitment types on the short side, and commitment types improve efficiency. In a balanced market where the entering flows of the two sides are equal, bargaining follows equilibrium play in a bargaining game with two-sided reputation and commitment types cause inefficiency. An inefficient equilibrium with persistent delays and break-ups is constructed. The magnitude of inefficiency is determined by the inflexible demands of the commitment types and is independent of the fraction of the commitment types entering the market.Bargaining, Reputation, Search, Dynamic Matching, War-of-Attrition. JEL Classification Numbers: C78, D83

Reputation in Long-Run Relationships

We model a long-run relationship as an infinitely repeated game played by two equally patient agents. In each period, the agents play an extensive-form game of perfect information. There is incomplete information about the type of player 1 while player 2’s type is commonly known. We show that a sufficiently patient player 1 can leverage player 2’s uncertainty about his type to secure his highest payoff in any perfect Bayesian equilibrium of the repeated game.Repeated Games, Reputation, Equal Discount Factor, Long-run Players. JEL Classification Numbers: C73, D83

Impermanent Types and Permanent Reputations

We study the impact of unobservable stochastic replacements for the long-run player in the classical reputation model with a long-run player and a series of short-run players. We provide explicit lower bounds on the Nash equilibrium payoffs of a long-run player, both ex-ante and following any positive probability history. Under general conditions on the convergence rates of the discount factor to one and of the rate of replacement to zero, both bounds converge to the Stackelberg payoff if the type space is sufficiently rich. These limiting conditions hold in particular if the game is played very frequently.Reputation, repeated games, replacements, disappearing reputations JEL Classification Numbers: D80, C73

Reputation and screening in a noisy environment with irreversible actions

We introduce a class of two-player dynamic games to study the effectiveness of screening in a principal-agent problem. In every period, the principal chooses either to irreversibly stop the game or to continue, and the agent chooses an action if the principal chooses to continue. The agent’s type is his private information, and his actions are imperfectly observed. Players’ flow payoffs depend on the agent’s action, and players’ lump-sum payoffs when the game stops depends on the agent’s type. Both players are long-lived and share a common discount factor. We study the limit of the equilibrium outcomes as both players get arbitrarily patient. Nash equilibrium payoff vectors converge to the unique Nash equilibrium payoff vector of an auxiliary, two-stage game with observed mixed actions. The principal learns some but not all information about the agent’s type. Any payoff-relevant information revelation takes place at the beginning of the game. We calculate the probability that the principal eventually stops the game, against each type of the agent

Reputation in Repeated Moral Hazard Games

We study an infinitely repeated game where two players with equal discount factors play a simultaneous-move stage game. Player one monitors the stage- game actions of player two imperfectly, while player two monitors the pure stage- game actions of player one perfectly. Player one’s type is private information and he may be a “commitment type,” drawn from a countable set of commitment types, who is locked into playing a particular strategy. Under a full-support assumption on the monitoring structure, we prove a reputation result for repeated moral hazard games: if there is positive probability that player one is a particular type whose commitment payoff is equal to player one’s highest payoff, consistent with the players’ individual rationality, then a patient player one secures this type’s commitment payoff in any Bayes-Nash equilibrium of the repeated game

Reputation in Repeated Moral Hazard Games

We study an infinitely repeated game where two players with equal discount factors play a simultaneous-move stage game. Player one monitors the stage- game actions of player two imperfectly, while player two monitors the pure stage- game actions of player one perfectly. Player one’s type is private information and he may be a “commitment type,” drawn from a countable set of commitment types, who is locked into playing a particular strategy. Under a full-support assumption on the monitoring structure, we prove a reputation result for repeated moral hazard games: if there is positive probability that player one is a particular type whose commitment payoff is equal to player one’s highest payoff, consistent with the players’ individual rationality, then a patient player one secures this type’s commitment payoff in any Bayes-Nash equilibrium of the repeated game

Learning from Manipulable Signals

We study a dynamic stopping game between a principal and an agent. The agent is privately informed about his type. The principal learns about the agent's type from a noisy performance measure, which can be manipulated by the agent via a costly and hidden action. We fully characterize the unique Markov equilibrium of this game. We find that terminations/market crashes are often preceded by a spike in (expected) performance. Our model also predicts that, due to endogenous signal manipulation, too much transparency can inhibit learning. As the players get arbitrarily patient, the principal elicits no useful information from the observed signal