A Noncooperative Model of Network Formation

TLDR

Social networks form through individual decisions that balance link costs against benefits, with links providing access to others’ benefits and generating externalities that depend on indirect link decay. The study proposes a model of network formation where individuals trade link costs against potential rewards. The model treats link costs as borne only by the initiator, enabling a noncooperative game formulation that characterizes equilibrium network architectures and their formation dynamics. The model predicts that individual link‑forming efforts quickly produce equilibrium networks with simple structures such as wheels or stars, many of which are socially efficient.

Abstract

We present an approach to network formation based on the notion that social networks are formed by individual decisions that trade off the costs of forming and maintaining links against the potential rewards from doing so. We suppose that a link with another agent allows access, in part and in due course, to the benefits available to the latter via his own links. Thus individual links generate externalities whose value depends on the level of decay/delay associated with indirect links. A distinctive aspect of our approach is that the costs of link formation are incurred only by the person who initiates the link. This allows us to formulate the network formation process as a noncooperative game. We first provide a characterization of the architecture of equilibrium networks. We then study the dynamics of network formation. We find that individual efforts to access benefits offered by others lead, rapidly, to the emergence of an equilibrium social network, under a variety of circumstances. The limiting networks have simple architectures, e.g., the wheel, the star, or generalizations of these networks. In many cases, such networks are also socially efficient.