“People interested in creating economic connectedness should equally focus on getting people with different incomes to interact,” Stroebel said.

Jimarielle Bowie grew up in a lower-middle-class family. Her parents divorced, lost jobs and lost homes. So when she made friends in high school with girls who lived on the rich side of town, their lifestyles intrigued her. Their houses were bigger; they ate different foods; and their parents — doctors and lawyers — had different goals and plans for their children, including applying for university.

“My mum really instilled working hard in us — being knowledgeable about our family history, you have to be better, you have to do better,” said Bowie, 24, who goes by Mari. “But I didn’t know anything about the SAT, and my friends’ parents signed up for this class, so I thought I should do that. I had friends’ parents look at my personal statements.”

Bowie became the first person in her family to get a postgraduate degree. She’s now a criminal defence lawyer — a job she found through a friend of one of those high school friends.

“My experience meeting people who were more affluent, I got to get in those circles, understand how those people think,” she said. “I absolutely think it made a significant difference.”

Social capital, the network of people’s relationships and how they are influenced by them, has long intrigued social scientists. The first known use of the phrase was in 1916, by LJ Hanifan, a school administrator in West Virginia. Since then, researchers have found that ties to more educated or affluent people, starting in childhood, can shape aspirations, college-going and career paths.

But the new study — using a significantly larger data set than other studies, covering 21 billion Facebook friendships — is the first to show that living in a place that fosters these connections causes better economic outcomes.

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The researchers found the more connections between the rich and poor, the better the suburb was at lifting children from poverty. After accounting for these connections, other characteristics that the researchers analysed — including the area’s racial composition, poverty level and school quality — mattered less for upward mobility, or not at all.

“It’s a big deal because I think what we lack in America today, and what’s been dropping catastrophically over the last 50 years, is what I call ‘bridging social capital’ — informal ties that lead us to people who are unlike us,” said Robert Putnam, the political scientist at Harvard who wrote “Bowling Alone” and “Our Kids,” about the decline of social capital in the United States.

“And it’s a really big deal because it provides a number of avenues or clues by which we might begin to move this country in a better direction.”

Other kinds of social capital matter, too, like rates of volunteering in a community and friendships with people from similar backgrounds. Yet the new study shows that even in places lacking in other kinds of social capital, an increase in cross-class relationships is enough to benefit children’s economic prospects.

This article originally appeared in The New York Times.

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