An Equivalence Theorem between geometric structures and utility functions allows new methods for understanding preferences. Our classification of valuations into “Demand Types” incorporates existing definitions (substitutes, complements, “strong substitutes,” etc.) and permits new ones....

Several partners jointly own an asset that may be traded among them. Each partner has a valuation for the asset. The valuations are known privately and drawn independently from a common probability distribution. The authors characterize the set of all incentive- compatible and interim...

The authors analyze the evolution of duopolists' prices and market shares in an infinite-period market with consumer switching costs in which in every period new consumers arrive and a fraction of old consumers leaves. They show prices (and profits) are higher than without switching costs and...