The Architecture of Social Networks and the Diffusion of Innovations

Abstract

For many technologies and behaviors, an agent’s benefit from adopting depends on his contacts adopting, and the benefit to his contacts of adopting depends on their contacts adopting. This paper examines how the architecture of these connections shapes the success or failure of the diffusion of innovations. We start with a standard model of diffusion with the key addition that some agents can coordinate their decisions. This captures the idea that people often talk and make decisions together with friends or family to adopt technologies. We show that insularity of connections, that is, the extent to which agents tend to concentrate their connections to a narrow set of other agents, determines contagion. However, whether insularity helps or hinders depends on the technology being diffused. For technologies that are valuable even without many contacts adopting, we find insular connections hinder adoption, but for technologies that are valuable only when many contacts adopt, insular connections facilitate adoption.