We develop a model of firm size in which firms are unable to access as many consumers as they want. Nwely arrived consumers match randomly with firms. Subsequently consumers must pay "search costs"to be able to switch firms.

The authors analyze a search-theoretic framework in which consumers buy the product repeatedly and firms' costs vary over time. They show the cross-sectional correlation between profits and firm size, the persistence of profits over time, and the role of consumers' immobility in determining...

We consider a durable-good monopolist that periodically introduces new models, each new model representing an improvement upon its predecessor. We show that if the monopolist is able neither to exercise planned obsolescence (i.e., artificially shorten the lift of its products) nor to give...