The key to landing your dream job might be connecting and then sending a single message to a casual acquaintance on social media..
That’s the conclusion of a five-year study of more than 20 million users on the professional networking site LinkedIn, the researchers report in the Sept. 16 issue. Sciences. The study is the first large-scale effort to experimentally test a nearly 50-year-old social science theory that says weak social ties they matter more than the strong to get ahead in life, even to find a good job.
“The weak link theory is one of the most celebrated and cited findings in the social sciences,” says network scientist Dashun Wang of Northwestern University in Evanston, Illinois, who is a co-author. a perspective piece in the same number of Sciences. This study “provides the first causal evidence for this idea of weak links explaining labor mobility.”
Sociologist Mark Granovetter of Stanford University proposed the weak-bind theory in 1973. The theory, which has garnered nearly 67,000 scientific citations, is based on the idea that humans are grouped into social spheres that connect through bridges (Serial number: 08/13/03). Those bridges represent weak social ties between people and give people who cross access to realms of new ideas and information, including about job markets.
But the influential theory has come under fire in recent years. Notably, a 2017 analysis in the Journal of labor economics of 6 million Facebook users showed that increasing interaction with a friend online, thereby strengthening that social bond, increased the probability of working with that friend.
In the new study, LinkedIn gave Sinan Aral, a managerial economist at MIT, and her team access to data from the company’s People You May Know algorithm, which recommends new connections to users. For five years, the social networking site’s operators used seven variations of the algorithm for users actively seeking connections, each of which recommended different levels of strong and weak links for users. During that time, the site saw 2 billion new links and 600,000 job changes.
Aral and her colleagues measured the strength of ties through the number of mutual LinkedIn connections and direct messages between users. Job transitions occurred when two criteria were met: a partner connected on LinkedIn at least one year before the job seeker joined the same company as the other user; and the user who first joined the company was there for at least a year before the second user joined. Those criteria were intended in part to rule out situations where the two might have ended up at the same company by chance.

In general, weak ties were more likely to lead to job changes than strong ones, the team found. But the study adds a twist to the theory: When looking for a job, mid-level friends are more helpful than close friends or strangers. Those are the friends you share about 10 connections with and rarely interact with, Aral says. “They are still weak ties, but they are not the weakest ties.”
The researchers also found that when a user added more weak links to their network, that person applied for more jobs overall, which translated into getting more jobs. But that finding applied only to highly digitized jobs, such as those that rely heavily on software and lend themselves to remote work. Strong ties were more beneficial than weak ties for some job seekers outside of the digital realm. Aral suspects that such jobs may be more local, and thus rely on members of tight-knit communities.
The finding that job seekers should lean on mid-level acquaintances corroborates smaller studies, says network scientist Cameron Piercy of the University of Kansas at Lawrence, who was not involved in either the 2017 study or this most recent one.
That evidence suggests that weaker acquaintances lack enough information about the job candidate, while closest friends know too much about the candidate’s strengths and flaws. “There’s this sweet spot of mid-ties where you’re willing to vouch for them because they know a couple of people you know,” says Piercy.
But he and others also raise ethical concerns about the new study. Piercy is concerned about research that manipulates people’s social media spaces without clearly and obviously indicating that it is being done. In the new study, LinkedIn users who visited the “My Network” page to get hookup recommendations, representing less than 5 percent of the site’s monthly active users, automatically opted into the experiment.
And it’s unclear how LinkedIn, whose researchers co-authored the study, will use this information in the future. “When you talk about people’s work, their ability to earn money, this is important,” says Piercy. The company “should recommend weak ties, the version of the algorithm that led to more job achievement, if its purpose is to connect people to work. But they do not come to that conclusion in the document.”
Another limitation is that the analyzed data lacked vital demographic information about users. That was for privacy reasons, the researchers say. But breaking down the results by gender is crucial, as some evidence suggests that women, but not men, should rely on both weak and strong ties for career advancement, says Northwestern’s Wang.
Still, with more than half of jobs typically found through social ties, the findings could point people toward better ways to look for a job in today’s tumultuous environment. “You may have seen these recommendations on LinkedIn and ignored them. You think ‘Oh, I don’t really know that person,’” says Aral. “But you may be doing yourself a disservice.”