Social capital—the strength of an individual’s social network and community—has been identified as a potential determinant of outcomes ranging from education to health^{1,2,3,4,5,6,7,8}. However, efforts to understand what types of social capital matter for these outcomes have been hindered by a lack of social network data. Here, in the first of a pair of papers⁹, we use data on 21 billion friendships from Facebook to study social capital. We measure and analyse three types of social capital by ZIP (postal) code in the United States: (1) connectedness between different types of people, such as those with low versus high socioeconomic status (SES); (2) social cohesion, such as the extent of cliques in friendship networks; and (3) civic engagement, such as rates of volunteering. These measures vary substantially across areas, but are not highly correlated with each other. We demonstrate the importance of distinguishing these forms of social capital by analysing their associations with economic mobility across areas. The share of high-SES friends among individuals with low SES—which we term economic connectedness—is among the strongest predictors of upward income mobility identified to date^10,11. Other social capital measures are not strongly associated with economic mobility. If children with low-SES parents were to grow up in counties with economic connectedness comparable to that of the average child with high-SES parents, their incomes in adulthood would increase by 20% on average. Differences in economic connectedness can explain well-known relationships between upward income mobility and racial segregation, poverty rates, and inequality^12,13,14. To support further research and policy interventions, we publicly release privacy-protected statistics on social capital by ZIP code at https://www.socialcapital.org.

社会资本——个人社交网络和社区的力量——已被确定为从教育到健康^{1,2,3,4,5,6,7,8}的潜在决定因素。然而，由于缺乏社交网络数据，了解哪些类型的社会资本对这些结果很重要的努力受到了阻碍。在这里，在一对论文中的第一篇⁹，我们使用来自 Facebook 的 210 亿个好友数据来研究社会资本。我们通过美国邮政编码来衡量和分析三种类型的社会资本：（1）不同类型的人之间的联系，例如社会经济地位（SES）低和高的人；(2) 社会凝聚力，例如友谊网络中派系的程度；(3) 公民参与，例如志愿服务的比率。这些指标在不同地区之间差异很大，但彼此之间的相关性并不高。我们通过分析它们与跨地区经济流动性的关联来证明区分这些形式的社会资本的重要性。社会经济地位低的个体中社会经济地位高的朋友的比例——我们称之为经济联系——是迄今为止确定的收入向上流动性最强的预测指标之一^10,11。其他社会资本衡量指标与经济流动性没有密切关联。如果低 SES 父母的孩子在经济联系程度与高 SES 父母的普通孩子相当的县长大，他们成年后的收入平均会增加 20%。经济联系的差异可以解释众所周知的收入向上流动与种族隔离、贫困率和不平等之间的关系^12,13,14。为了支持进一步的研究和政策干预，我们在 https://www.socialcapital.org 上按邮政编码公开发布受隐私保护的社会资本统计数据。