If you’re like me, you could use at least a brief break from talking about Donald Trump. So why don’t we talk about Ivanka Trump instead? You see, recently she said something that would have been remarkable coming from any Republican, but was truly awesome coming from the Daughter in Chief.

The subject under discussion was the proposal, part of the Green New Deal, that the government offer a jobs guarantee. Ms. Trump trashed the notion, claiming that Americans “want to work for what they get,” that they want to live in a country “where there is the potential for upward mobility.”

O.K., this was world-class lack of self-awareness: It doesn’t get much better than being lectured on self-reliance by an heiress whose business strategy involves trading on her father’s name. But let’s go beyond the personal here. We know a lot about upward mobility in different countries, and the facts are not what Republicans want to hear.

The key observation, based on a growing body of research, is that when it comes to upward social mobility, the U.S. is truly exceptional — that is, it performs exceptionally badly. Americans whose parents have low incomes are more likely to have low incomes themselves, and less likely to make it into the middle or upper class, than their counterparts in other advanced countries. And those who are born affluent are, correspondingly, more likely to keep their status.