This paper reports results of an experiment designed to investigate the nature of cooperation and punishment. Subjects are matched in a series of two-person, two-stage games with a sequential equilibrium that supports first-stage cooperation with a credible threat of subsequent punishment....

Many aspects of antitrust policy are influenced by the possibility that sellers in concentrated markets may have the power to raise prices above competitive levels. Of course, anyone can raise prices, so the issue is whether a change in structure, e.g., a merger, will allow one or more sellers...

Market power arises in many posted-offer markets and drives a distinction between the competitive prediction and the Nash equilibrium for the market viewed as a stage game. Pricing patterns in such markets tend to be characterized by Edgeworth cycles that deteriorate as the sessions progress....