This paper develops a model of pricing to deter entry by a sole supplier of
a network good. We show that the installed user base of a network good can
serve a preemptive function similar to that of an investment in capacity i
f the entrant's good is incompatible with the incumbent's good and there ar
e network externalities in demand. Consequently, the threat of entry can le
ad the incumbent to set low prices, We identify some factors that should be
considered in thinking about the welfare effects of entry deterrence in th
is and similar models.