Despite the pervasive phenomenon of scale economies the majority of firms hasalways been small firms. The emergence of small firms as a means of economic development on both sides of the Atlantic has been one of the major new topics of economic policy since the 1980s. This has drawn renewed...

We extend the models in ("Competition in two-sided markets" of Armstrong (2006, Rand Journal of Economics) by adding within-group externalities. In the monopoly and duopoly cases, positive within-group externalities reduce the price of the own group. Negative externalities have an opposite price...