But Granovetter’s analysis showed that people actually got new jobs most frequently through friends of friends-often someone the job seeker had not known before they started looking for a new position. Before his groundbreaking paper, many had assumed that new positions came from sources such as close personal friends who would put in a good word, headhunters who would seek out strong candidates or public advertisements. For the original 1973 research, Granovetter interviewed people late in their career and asked them about their experiences with job changes.

The strength of weak ties “is really a cornerstone of social science,” says Dashun Wang, a professor at the Kellogg School of Management at Northwestern University, who was not involved in the new study. And it reveals which types of connections are most important for job hunters.

Now a sweeping study that looked at more than 20 million people on the professional social networking site LinkedIn over a five-year period finally shows that forging weak ties does indeed help people get new jobs. But the theory, dubbed “the strength of weak ties,” after the title of Granovetter’s study, lacked causal evidence for decades. Sociologist Mark Granovetter first laid out this idea in a 1973 paper that has garnered more than 65,000 citations. According to one of the most influential theories in social science, you’re more likely to nab a new position through your “ weak ties,” loose acquaintances with whom you have few mutual connections. If you want a new job, don’t just rely on friends or family.

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