经济学家Raj Chetty团队基于Facebook的21亿个友谊关系数据，对72万美国人进行了研究，发现经济连通性——即个人朋友中比自己收入高的比例——是预测向上流动性最强的指标[1]。童年期间拥有高经济连通性的人成年后平均收入高20%，这一效应的预测力度超过学校质量、种族隔离和贫困率等传统因素[1]。
研究揭示了不同收入群体之间的社交鸿沟[1]。底层收入人群中，不足2%的朋友属于前10%收入者，而顶层收入人群中，这一比例达到34%[1]。这种经济连通性的差异直接影响了个人的职业前景和收入潜力。
弱关系和偶然接触在就业流动性中发挥了关键作用[1]。1973年的一项调查发现，56%的男性通过偶尔见面的接触找到工作[1]。这一发现在近期得到进一步验证：2022年LinkedIn进行的一项涉及2000万用户的随机实验证实了弱关系对就业流动性的因果效应[1]。
Economist Raj Chetty's team has identified economic connectedness—the proportion of a person's friends who earn more than they do—as the strongest predictor of upward mobility, based on analysis of 2.1 billion Facebook friendships across 720,000 Americans [1]. Children who maintain high economic connectedness during their formative years go on to earn approximately 20% more as adults, a correlation that outweighs the effects of school quality, racial segregation, and poverty rates [1].
The research reveals stark disparities in social networks across income levels [1]. Among those in the bottom income tier, fewer than 2% of their friends belong to the top 10% of earners, while 34% of the top earners' friends come from the same elite income group [1]. Beyond direct friendships, the study underscores the importance of weak ties and chance encounters for employment mobility [1]. A 1973 survey found that 56% of men secured jobs through occasional contacts rather than close relationships [1]. This finding was corroborated by a 2022 LinkedIn randomized experiment involving 20 million users, which confirmed the causal effect of weak social connections on employment outcomes [1].