We present a general Cournot model in which each ¯rm may sell multiplequality-di®erentiated products. We use an upgrades approach, working not with theactual products, but instead with upgrades from one quality to the next. The prop-erties of single-product Cournot models carry over to the...

We propose a framework for analyzing transformations of demand. Such transformations frequently stem from changes in the dispersion of consumers` valuations, which lead to rotations of the demand curve. In a wide variety of settings, profits are a U-shaped function of dispersion. A high level of...

We present a general Cournot model in which each firm may sell multiple quality-differentiated products. We use an upgrades approach, working not with the actual products, but instead with upgrades from one quality to the next. The properties of single-product Cournot models carry over to the...

Firms selling multiple quality-differentiated products frequently alter their product lines when a competitor enters the market. We present a model of multiproduct monopoly and duopoly using a general `upgrades` approach that yields a powerful analytical framework. We provide a simple...