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...

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...

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 an explanation for...

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 many settings, profits are a U-shaped function of dispersion. High dispersion is...

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...

A simple model of open source software (as typified by the GNU-Linux operating system) is presented. Individual user-programmers decide whether to invest their own effort to develop a software enhancement that will become a public good if so developed. The effect of changing the population size...

Dynamic motivations for the use of product line extensions in the form of entry-level products are considered. When consumers are uncertain of their valuations for products, and their purchasing power evolves over time, firms competing in a lucrative luxury market may try to influence the future...

An economy is considered in which new firms require time to learn whether they will grow in size and profitability in the long run. The labor market is imperfectly competitive. I show that inefficient levels of firm entry will generally exist. Whether under or over entry occurs is tightly...