Multiproduct Duopoly With Vertical Differentiation
The paper investigates a two-stage competition in a vertical differentiated industry, where each firm produces an arbitrary number of similar qualities and sells them to heterogeneous consumers. The authors show that, when unit costs of quality are increasing and quadratic, each firm has an incentive to provide an interval of qualities. The finding is in sharp contrast to the single-quality outcome when the market coverage is exogenously determined. They also show that allowing for an interval of qualities intensifies competition, lowers the profits of each firm and raises the consumer surplus and the social welfare in comparison to the single-quality duopoly.