The paper found that a highly educated professional has a 57 percent probability of reading prestige newspapers (“broadsheets”) if their best friend is also an educated professional.

But if their best friend is a blue-collar laborer, then the probability drops to 32 percent.

Not reading such newspapers, though, is in fact, a barrier to upward mobility. Not having some awareness of the etiquette of the educated classes can impede success in white-collar occupations.

So if an upwardly mobile working-class person maintains ties with old friends, and retains some of the same cultural habits, it will become harder for them to integrate into a new class.

How many low-income people want to lose contact with their old friends for a shot at upward mobility? Very few. If I had known in advance that this would happen, however gradually, I may have made different choices. I felt a deep bond with my friends growing up, and still do, even as the distance between us grows.