We revisit the fundamental issue of market provision of variety associated with Chamberlin, Spence, and Dixit and Stiglitz when firms sell several products. Both products and firms are envisaged as di?erentiated. We propose a nested demand model where consumers decide upon a firm then which...

We describe firm pricing when consumers search passively and follow simple reservation price rules. In stark contrast to other models in the literature, this approach yields equilib- rium price dispersion in pure strategies even when firms have the same marginal costs. In equilibrium, lower...

We analyze an oligopoly model with horizontal di¤erentiation and quality di¤erences. High quality goods are over-priced and under-produced. When the market is fairly covered, low quality products may be pro…table when their social contribution is negative, leading to too many products in...

Advertising messages compete for scarce attention. ?Junk? mail, ?spam? e-mail, and telemarketing calls need both parties to exert effort to generate transactions. Message recipients supply attention depending on average message beneÞt. Senders are motivated by proÞts. Costlier message...

We consider commuting in a congested urban area. While an efficient time-varying toll may eliminate queuing, a toll may not be politically feasible. We study the benefit of a substitute: a parking fee at the workplace. An optimal time-varying parking fee is charged at zero rate when there is...

We formulate a family of direct utility functions for the consumption of a differentiated good. This is used to generate a family of demand systems with flexible substitution patterns. Demand models for market shares can be estimated by regression enabling the use of instrumental variables....

We consider dynamic congestion in an urban setting where trip origins are spatially distributed. All travelers must pass through a downtown bottleneck in order to reach their destination in the CBD. Each traveler chooses departure time to maximize general concave scheduling utility. We find...

We analyse Nash equilibrium in time of use of a congested facility. Users are risk averse with general concave utility. Queues are subject to varying degrees of random sorting, ranging from strict queue priority to a completely random queue. We define the key "no residual queue" property, which...