A substantial portion of information goods is sold through upgrades. I model a monopolist offering successive generations of an information good in a dynamic model. In each period, the monopolist offers up to two prices for each generation: a full price to those who have never purchased and a...

We test the effect of entry on the tariff choices of incumbent cellularfirms. We relate the change in the breadth of calling plans between1996, when incumbents enjoyed a duopoly market, and 1998, whenincumbents faced increased competition from personal communicationsservices (PCS) firms. Entry...