At least some of this has to do with convenience. Whereas higher-earning households are freer to outsource domestic tasks, Americans with less income tend to need the help provided by family members and those close by, be it in the form of money, childcare or care for the elderly, signing for UPS packages, or having two people to turn the ladder while they hold a new lightbulb in place.

“For people with limited financial resources, these social ties are likely to be crucial for managing existing and impending challenges,” Bianchi and Vohs wrote. “Hence, people with limited resources might be particularly attuned to the relationships that are most strongly associated with giving and receiving instrumental support.”

Bianchi says she was surprised by the extent to which income can predict social habits. “We know that generally income or at least access to money in an experimental context is associated with less time or less interest in others,” says Bianchi. “So, on the one hand, we thought that income would negatively predict time spent with friends. On the other hand, it’s a luxury. You can choose your friends—you can’t choose your family. Neighbors are somewhere in between. But certainly, friendships are our most voluntary type of social tie.”

A 2015 University of Michigan study found that Americans who live far from their mothers are more likely to have more money and a better education, but Bianchi and Vohs found their pattern to hold even when high earners lived near their moms. “There’s no question that income does predict whether you live farther away from your parents,” Bianchi says. “But even if you do live close to your parents or your extended family, income still predicts how much time you’ll spend with them.”

So what then are the potential implications of having a more insular upper class? While the study doesn’t measure any such effects, this dynamic could lead to a decline in civic engagement. “If the wealthy are orienting their social worlds towards friends and away from neighbors and relatives, it seems likely that they also would be less involved in their residential communities,” Bianchi says. She adds, “Wealthier people may be less civically engaged with their neighborhood communities and more civically engaged with self-selected communities such as private schools or political organizations.”

At a time when Americans are becoming more economically stratified, it’s worrying that the highest earners might be less likely to have a sense of what’s going on outside of their own peer groups—and that it’s easier to be Richie Rich as well as Home Alone.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.