“Weak ties” between individuals have the greatest impact on job mobility

A friend of a friend or acquaintance may be more helpful in finding a new, higher-paying job than a close friend or family member, researchers report. The study uses data from LinkedIn – the world’s largest professional social network – and provides experimental causal evidence supporting the so-called “strength of weak ties” social theory. The strength of weak ties is an influential social-scientific theory, which stresses the importance of weak associations – acquaintances versus close friendships, for example – in shaping the transmission of information through social networks. Among other social phenomena, this theory has been used to explain why the most useful contacts in landing a better job are not close friends or family but rather those in our social networks least expected to be capable, or willing, to help. These “weak ties” are thought to provide access to diverse and novel information because they bridge otherwise disconnected social circles. Although strength of weak ties theory has become a cornerstone in modern social science, causal tests of this theory have proved challenging. What’s more, recent large-scale correlational studies have produced conflicting findings, leading to a seeming “paradox of weak ties.” Using data from LinkedIn, Karthik Rajkumar and colleagues evaluated strength of weak ties theory. Leveraging experimental variations in LinkedIn’s key features, the so-called “People You May Know” algorithm, which recommends new connections to users, Rajkumar et al. tracked the effect of weak ties in the social networks of more than 20 million people over a five-year period, during which 2 billion new ties and 600,000 new jobs were recorded. Overall, the authors found that the weakest ties had the greatest impact on job mobility while the strongest ties had the least. However, although weak ties did increase job transmissions, they only did so to a point, after which diminishing returns to tie weakness were observed. Moreover, according to the findings, the strength of weak ties varied by industry – while weak ties increased job mobility in more high-tech industries, they had less of an effect in job mobility on low-tech industries. In a related Perspective, Dashun Wang and Brian Uzzi discuss the study’s findings in greater detail and highlight avenues for future research, including studies focused on how social networks sustain failures and promote inequality.