The muddier question is who those people are—and whether, as Sachs and Kotlikoff suggest, younger people are among the groups being harmed. “There is much to the Sachs and Kotlikoff paper, but I don’t view it mainly as an old vs. young effect,” says economist Tyler Cowen. It may not make sense to assume that young people are the unskilled ones: “The key question is who works well with computers and who is competing with computers,” Cowen says. Often, he points out, technological change favors the young—just look at Mark Zuckerberg—so it’s perhaps too simple to group young people as one unskilled mass.

Of course, Zuckerbergs are not the norm. “There are a lot of young people to whom this model actually applies. Probably more than half of young people,” drawn, for instance, from the two-thirds of 25- to 29-year-olds without bachelor degrees, says Sachs. “If our labor force was all young computer programmers, we probably wouldn’t be having this discussion, period.”

Sachs and Kotlikoff are economists, not revolutionaries; they aren’t Luddite enough to want to smash the machines. Instead, they suggest a mechanism for making sure benefits are more evenly shared—in this case, a redistributive tax. Other economists think that it’s still possible to get people the right education to do the jobs robots can’t.