For poor children, living in an area where people have more friendships that cut across class lines significantly increases how much they earn in adulthood, the new research found.

The study, published Monday in Nature, analyzed the Facebook friendships of 72 million people, amounting to 84 percent of U.S. adults aged 25 to 44.

Previously, it was clear that some neighborhoods were much better than others at removing barriers to climbing the income ladder, but it wasn’t clear why. The new analysis — the biggest of its kind — found the degree to which the rich and poor were connected explained why a neighborhood’s children did better later in life, more than any other factor.

The effect was profound. The study found that if poor children grew up in neighborhoods where 70 percent of their friends were wealthy — the typical rate of friendship for higher-income children — it would increase their future incomes by 20 percent, on average.

These cross-class friendships — what the researchers called economic connectedness — had a stronger impact than school quality, family structure, job availability or a community’s racial composition. The people you know, the study suggests, open up opportunities, and the growing class divide in the United States closes them off.

Vast New Study Shows a Key to Reducing Poverty, Claire Cain Miller, Josh Katz, Francesca Paris and Aatish Bhatia, New York Times, August 1, 2022, available here