Socializing Alone: How Online Homophily Has Undermined Social Cohesion in the US

Online social networks have changed how people interact across large distances. We examine the long-run effect of a key feature of these networks --- online homophily --- on interpersonal interactions in local communities. Using Facebook data, we measure online homophily across counties in the United States. To identify effects, we exploit a conflict between Facebook and Google over data sharing of user information in the early expansion phase of Facebook, which induced persistent variation across counties. We find evidence that these homophilic connections on Facebook made people spend more time on the platform but socialize less \textit{offline}, as measured through bar, restaurant, and live sports event visits. The effects are substantial: we estimate that a one-standard-deviation increase in online homophily is associated with approximately a 25 percent reduction in offline socialization. This effect was accompanied by a negative effect on local social capital by making individuals less connected across income strata. Moreover, political opinions within counties became less homogeneous, with a lowered probability that two voters in a county support the same political party. Overall, our results indicate that when a natural demand for connecting with socially similar people is met by the supply of a `death-of-distance' technology, it comes at the cost of social cohesion at the local level.