Network externalities spur the growth of networks and the adoption of network goods in two ways. First, they make it more attractive to join a network the larger its installed base. Second, they create incentives for network members to actively recruit new members. Despite indications that the latter “peer effect” can be more important for network growth than the installed-base effect, it has so far been largely ignored in the literature. We address this gap using game-theoretical models. When all early adopters can band together to exert peer influence—an assumption that fits, e.g., the case of firms supporting a technical standard—we find that the peer effect induces additional growth of the network by a factor. When, in contrast, individuals exert peer influence in small groups of size n, the increase in network size is by an additive constant—which, for small networks, can amount to a large relative increase. The difference between small, local, personal networks and large, global, anonymous networks arises endogenously from our analysis. Fundamentally, the first type of networks is “tie-reinforcing,” the other, “tie-creating”. We use survey data from users of the Internet services, Skype and eBay, to illustrate the main logic of our theoretical results. As predicted by the model, we find that the peer effect matters strongly for the network of Skype users—which effectively consists of numerous small sub-networks—but not for that of eBay users. Since many network goods give rise to small, local networks, our findings bear relevance to the economics of network goods and related social networks in general. Copyright Springer-Verlag Berlin Heidelberg 2013
