Through Trial and Error to Collusion*

In this article we study a very simple trial and error learning process in the context of a Cournot oligopoly. Without any knowledge of the payoff functions players increase, respectively decrease, their quantity as long as this leads to higher profits. We show that despite the absence of any coordination or punishing device this process converges to the joint‐profit‐maximizing outcome.     

Vertical Integration and Market Foreclosure with Convex Downstream Costs

Received December 14, 2000; revised version received July 16, 2001     

Endogenous cartel formation: Experimental evidence

In a Bertrand-oligopoly experiment, firms choose whether or not to engage in cartel-like communication and, if so, they may get fined by a cartel authority. We find that the four-firm industries form cartels more often than the duopolies because they gain less from a hysteresis effect after cartel disruption.     

Shrouding Add‐On Information: An Experimental Study*

We explore how increased competition affects firms’ obfuscation strategies in a laboratory experiment. Firms sell a base good and an add‐on product. Besides choosing the base‐good price, sellers take an action that mimics the effects of shrouding the add‐on product. Shrouding is an equilibrium but an unshrouding equilibrium coexists. In our experiment, more competition matters, in that only duopolistic markets are frequently shrouded whereas four‐firm markets are not. With repeated interaction, shrouding rates do not increase. However, the opportunities to shroud facilitate tacit collusion on the base‐good price for the duopolies: the unshrouding equilibrium serves as a credible punishment if deviations occur.     

Endogenous Timing with Incomplete Information and with Observable Delay

This paper analyzes endogenous timing in a duopoly model with incomplete information. Firms announce the period in which they will move before choosing an action and are then committed to their choices. Endogenous Stackelberg equilibria, with either the informed or the uninformed firm as the Stackelberg leader, may emerge. For most parameters, the Cournot equilibrium in the first production period results endogenously. Journal of Economic Literature Classification Numbers: C72; C73; D82; L10.     

Simulating Ruin Probabilities for a Class of Semimartingales by Importance Sampling Methods

We consider the problem of finding the probability of ruin when the risk process is assumed to be a special semimartingale with absolutely continuous characteristics. We show how the generalized Girsanov theorem can be used in connection with Monte Carlo simulation to obtain estimates of the ruin probabilities. It is shown by both analytical and numerical examples that these methods can be significantly better than ordinary simulations provided the new measure is chosen with some care.     

Explicit vs. tacit collusion—The impact of communication in oligopoly experiments

We explore the difference between explicit and tacit collusion by investigating the impact communication has in experimental markets. For Bertrand oligopolies with various numbers of firms, we compare pricing behavior with and without the possibility to communicate among firms. We find strong evidence that talking helps to obtain higher profits for any number of firms, however, the gain from communicating is non-monotonic in the number of firms, with medium-sized industries having the largest additional profit from talking. We also find that industries continue to collude successfully after communication is disabled. Communication supports firms in coordinating on collusive pricing schemes, and it is also used for conflict mediation.     

Why factors facilitating collusion may not predict cartel occurrence — experimental evidence

Factors facilitating collusion may not successfully predict cartel occurrence: When a factor predicts that collusion (explicit and tacit) becomes easier, firms might be less inclined to set up a cartel simply because tacit coordination already tends to go in hand with supra-competitive profits. We illustrate this issue with laboratory data. We run n-firm Cournot experiments with written cheap-talk communication between players and we compare them to treatments without the possibility to talk. We conduct this comparison for two, four, and six firms. We find that two firms indeed find it easier to collude tacitly but that the number of firms does not significantly affect outcomes with communication. As a result, the payoff gain from communication increases with the number of firms, at a decreasing rate.     

Asymmetric Enforcement of Cooperation in a Social Dilemma

We use a public‐good experiment to analyze behavior in a decentralized asymmetric punishment institution. The institution is asymmetric in the sense that players differ in the effectiveness of their punishment. At the aggregate level, we observe remarkable similarities between outcomes in asymmetric and symmetric punishment institutions. Controlling for the average punishment effectiveness of the institutions, we find that asymmetric punishment institutions are as effective in fostering cooperation and are as efficient as symmetric institutions. At the individual level, we find that players with higher punishment effectiveness contribute similar amounts to the public account but have higher earnings and punish more than their weak counterparts.     

Identifying Laffer Bounds: A Sufficient‐Statistics Approach with an Application to Germany

We derive a simple sufficient‐statistics test for whether a nonlinear tax‐transfer system is second‐best Pareto efficient. If it is not, then it is beyond the top of the Laffer curve and there exists a tax cut that is self‐financing. The test depends on the income distribution, extensive and intensive labor supply elasticities, and income effect parameters. A tax‐transfer system is likely to be inefficient if marginal tax rates are quickly falling in income. We apply this test to the German tax‐transfer system, and we find that the structure of effective marginal tax rates is likely to be inefficient in the region where transfers are phased out.