Peter Ockenfels

Measuring Strategic Uncertainty in Coordination Games

This paper explores three aspects of strategic uncertainty: its relation to risk, predictability of behavior and subjective beliefs of players. In a laboratory experiment we measure subjects’ certainty equivalents for three coordination games and one lottery. Behavior in coordination games is related to risk aversion, experience seeking, and age. From the distribution of certainty equivalents we estimate probabilities for successful coordination in a wide range of games. For many games, success of coordination is predictable with a reasonable error rate. The best response to observed behavior is close to the global-game solution. Comparing choices in coordination games with revealed risk aversion, we estimate subjective probabilities for successful coordination. In games with a low coordination requirement, most subjects underestimate the probability of success. In games with a high coordination requirement, most subjects overestimate this probability. Estimating probabilistic decision models, we show that the quality of predictions can be improved when individual characteristics are taken into account. Subjects’ behavior is consistent with probabilistic beliefs about the aggregate outcome, but inconsistent with probabilistic beliefs about individual behavior.

Efficiency by trust in fairness? multiperiod ultimatum bargaining experiments with an increasing cake

Previous ultimatum bargaining experiments have shown that bargainers face the conflict whether to exploit bargaining power or to comply with basic norms of distributive justice. In multiperiod ultimatum bargaining for an increasing cake, trust in fairness can enable cooperation and thus more efficient results but is also open to opportunistic exploitation. In such a game the two players take turns in being the one who suggests an agreement and decides whether this is the final proposal, whereas his partner can only accept this proposal or reject it. While the game theoretic solution implies an immediate agreement assigning nearly all the cake to the demanding player, efficiency requires to postpone the agreement to the last possible round. Our 2 × 2-factorial design varies the number of possible bargaining periods and the cake increase, allowing us to explore several hypotheses.

Speculative Attacks and Financial Architecture:Experimental Analysis of Coordination Games with Public and Private Information

Speculative Attacks can be modeled as a coordination game with multiple equilibria if the state of the economy is common knowledge. With private information there is a unique equilibrium. This raises the question whether public information may be destabilizing by allowing for self-fulfilling beliefs. We present an experiment that imitates a speculative attacks model and compare sessions with public and private information. In both treatments subjects use so-called threshold strategies that lie in between the risk dominant and payoff dominant equilibrium of the underlying complete information game. Our evidence suggests that there are no destabilizing effects due to public information. In contrary, predictability of attacks is slightly higher with public than with private information, but prior probability of attacks is also higher with public information. We also test the predictive power of refinement theories to explain actual behavior and reactions to parameter changes.

On durable goods monopolies an experimental study of intrapersonal price competition and price discrimination over time

In a durable monopoly market a single seller can offer his product for sale in subsequent periods. A customer, however, will buy at most once. Solutions to such games have been derived in another study (Guth and Ritzberger, 1992), both for finitely and infinitely many sales periods. We report on classroom experiments with two or three potential sales periods and different constellations of discount factors. Game theory predicts for those cases either intrapersonal price competition (Coase-conjecture) or price discrimination (Pacman-conjecture). An experimental variation is that one group of participants was introduced to the theory of durable goods monopolies, whereas another group was completely unfamiliar with this theory and game theory in general.

Measuring Ambiguity Aversion: A Systematic Experimental Approach

This paper provides a systematic analysis of individual attitudes towards ambiguity, based on laboratory experiments. The design of the analysis allows to capture individual behavior across various levels of ambiguity, ranging from low to high. Attitudes towards risk and attitudes towards ambiguity are disentangled, providing pure measures of ambiguity aversion. Ambiguity aversion is captured in several ways, i.e. as a discount factor net of a risk premium, and as an estimated parameter in a generalized utility function. We find that ambiguity aversion varies across individuals, and with the level of ambiguity, being most prominent for intermediate levels. Around one third of subjects show no aversion, one third show maximum aversion, and one third show intermediate levels of ambiguity aversion, while there is almost no ambiguity seeking. While most theoretical work on ambiguity builds on maxmin expected utility, our results provide evidence that MEU does not adequately capture individual attitudes towards ambiguity for the majority of individuals. Instead, our results support models that allow for intermediate levels of ambiguity aversion. Moreover, we find risk aversion to be statistically unrelated to ambiguity aversion on average. Taken together, the results support the view that ambiguity is an important and distinct argument in decision making under uncertainty.