“A Causal Test of the Strength of Weak Ties”, Karthik Rajkumar, Guillaume Saint-jacques, Iavor Bojinov, Erik Brynjolfsson, Sinan Aral2022-09-15 (economics, sociology of tech)⁠:

[Perspective] The influence of weak associations: The strength of weak ties is an influential social-scientific theory that stresses the importance of weak associations (eg. acquaintance versus close friendship) in influencing the transmission of information through social networks. However, causal tests of this paradoxical theory have proved difficult. Rajkumar et al 2022 address the question using multiple large-scale, randomized experiments conducted on LinkedIn’s “People You May Know” algorithm, which recommends connections to users (see the Perspective by Wang & Uzzi2022). The experiments showed that weak ties increase job transmissions, but only to a point, after which there are diminishing marginal returns to tie weakness. The authors show that the weakest ties had the greatest impact on job mobility, whereas the strongest ties had the least. Together, these results help to resolve the apparent “paradox of weak ties” and provide evidence of the strength of weak ties theory.

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The authors analyzed data from multiple large-scale randomized experiments on LinkedIn’s People You May Know algorithm, which recommends new connections to LinkedIn members, to test the extent to which weak ties increased job mobility in the world’s largest professional social network.

The experiments randomly varied the prevalence of weak ties in the networks of over 20 million people over a 5-year period, during which 2 billion new ties and 600,000 new jobs were created.

The results provided experimental causal evidence supporting the strength of weak ties and suggested 3 revisions to the theory:

1. First, the strength of weak ties was nonlinear.

   Statistical analysis found an inverted U-shaped relationship between tie strength and job transmission such that weaker ties increased job transmission but only to a point, after which there were diminishing marginal returns to tie weakness.

2. Second, weak ties measured by interaction intensity and the number of mutual connections displayed varying effects.

   Moderately weak ties (measured by mutual connections) and the weakest ties (measured by interaction intensity) created the most job mobility.

3. Third, the strength of weak ties varied by industry.

   Whereas weak ties increased job mobility in more digital industries, strong ties increased job mobility in less digital industries.