We discuss the incentive of an exclusive holder of a technology to share it with competitors in a market with network externalities. We assume that high expected sales increase the willingness to pay for the good. This is named the "network effect". At a stable fulfilled expectations equilibrium, where the actual sales are equal to the expected ones, it is shown that, if the network effect is sufficiently strong, a quantity leader has an incentive to invite entry and license his technology without charge. If the quantity leader has the opportunity to use lump sum license fees, he will invite a larger number of competitors. If no lump sum fees are allowed, the leader will charge a decreasing fee in the intensity of the network externality and will invite entry. In markets with very strong network externalities, the leader pays a subsidy to the invited followers. We also show that the results hold under uncertainty, and when the post-entry competition is Cournot.

Key words: Network externalities, monopoly, quantity leadership, entry, licensing.

Published in the special issue of The European Journal of Political Economy on The Economics of Standardization (1996).

in Acrobat format. If you do not have an Acrobat reader, you can download it free from Adobe.