This paper discusses a model of vertical and horizontal product differentiation within the Dixit-Stiglitz framework of monopolistic competition. Firms compete not only in prices and horizontal attributes of their products, but also in the quality that can be controlled by R&D activities. Based...

Recent empirical evidence suggests that prices for some goods and services are higher in larger markets. This paper provides a demand-side explanation for this phenomenon when firms can choose how much to differentiate their products in a model of monopolistic competition with horizontal product...

The impact of product variety on welfare has received little attention in the electronic commerce literature. The problem with product variety is that more variety does not necessarily imply higher welfare. This paper finds the conditions under which more variety, if caused by lower fixed costs,...