The paper provides several axiomatizations of the concept of "path independence" as applied to choice functions defined over finite sets. The axioms are discussed in terms of their relationship to "rationality" postulates and their meaning with respect to social choice models.

Consider a committee or society attempting to order the alternatives (X_1, X_2, X_3) by use of majority rule. Each individual is assumed to have a strong ordering (called a profile) on the alternatives. "Indifference" is not a property of the profiles. The committee is said to "prefer" X_i to X_j, denoted X_iCX_j if X_i is preferred to X_j on a majority of the individual profiles. It is well known that if certain individual profiles are chosen, the resulting "social ordering" may be cyclical, i.e., X_iCX_j, X_jCX_k, X_kCX_i. Such a result is called a "cycle."

In a series of eleven markets, sellers possessed products that were exogenously designated as either grade "regular" or grade "super." Supers were valued more by buyers but grade could not be observed by buyers prior to purchase. Sellers could add costly units of quality to their products that were observable and valued by buyers. The data are analyzed with perfect information models, signaling equilibrium models, and pooling models. A variety of behaviors are observed across the eleven markets. Signaling is observed in most markets with some markets approaching the most efficient signaling equilibrium. Pooling or partial pooling occurs in a few markets. The performance seems to be sensitive to the relative cost of signaling and the market institutional setting.

The idea that markets might aggregate and disseminate information and also resolve conflicts is central to the literature on decentralization (Hurwicz, 1972) and rational expectations (Lucas, 1972). We report on three series of experiments all of which were predicted to have performed identically by the theory of rational expectations. In two of the three series (one in which participants trade a complete set of Arrow-Debreu securities and a second in which all participants have identical preferences), double auction trading leads to efficient aggregation of diverse information and rational expectations equilibrium. Failure of the third series to exhibit such convergence demonstrates the importance of market institutions and trading instruments in achievement of equilibrium.

We report the results of an experiment designed to study the role of speculation in the formation of bubbles and crashes in laboratory asset markets. In a setting in which speculation is not possible, bubbles and crashes are observed. The results suggest that the departures from fundamental values are not caused by the lack of common knowledge of rationality leading to speculation, but rather by behavior that itself exhibits elements of irrationality. Much of the trading activity that accompanies bubble formation, in markets where speculation is possible, is due to the fact that there is no other activity available for participants in the experiment.

The time path of asset prices is studied within a stationary experimental environment. After several replications prices converge to a perfect foresight equilibrium. A sequential market having an "informational trap" and a futures market are also studied.