The big picture: The study authors did a first-of-its-kind analysis of 72 million Facebook friendships between U.S. adults.

What they found: If poor children grew up in neighborhoods in which 70% of their friends were rich, their future incomes would be 20% higher than their counterparts who grew up without these bonds across class lines.

This was a stronger indicator of future income than factors like family structure and school quality, as well as the racial makeup and job availability in the child’s community.

Reality check: It’s not that simple. Friendships across class are increasingly hard to come by in our divided country.

For example, for people in the bottom 10% of the income distribution, only 2.5% of their friends are in the top 10%, Johannes Stroebel, an economist at NYU and one of the study authors, tells Axios.