Social capital I: measurement and associations with economic mobility

Recent work has argued that social capital may play a central role in shaping important social phenomena such as income inequality and economic opportunity. However, a lack of large-scale data on social networks has limited the ability of researchers to understand what types of social capital matter for such outcomes and how we can increase effective forms of social capital. For example, the most widely used dataset to study social networks—the National Longitudinal Study of Adolescent to Adult Health (Add Health)—covers approximately 20,000 students at 132 schools in the United States and, owing to small sample sizes, cannot be disaggregated by school. More recent studies have used large-scale mobile phone data to measure ‘experienced segregation’ but do not directly observe social interactions between different types of people, a distinction that we show is empirically important.

Here, we use data on the social networks of 72.2 million users of Facebook aged between 25 and 44 years to construct and publicly release (https://www.socialcapital.org) new measures of social capital for each ZIP code in the United States. In a companion paper, we also release data on social capital for each high school (secondary school) and college (university). As in previous research using Facebook data (Supplementary Information C.1), we use social network data as a proxy for real-world friendships rather than online interactions per se. As a result, our analysis does not shed light on the effects of online social networks themselves.

We correlate our new measures of social capital with data on economic mobility—children’s chances of rising up the income distribution—across areas and analyse the mechanisms through which social capital and economic mobility are related. We find that the degree to which people with low and high SES are friends with each other (which we term economic connectedness (EC)) is strongly associated with upward income mobility, whereas other forms of social capital are not.