This doesn't contradict Roberts. The chart at the top of your linked article shows that even for Gen X, poor people generally out earn their parents, and rich people are far less likely to out earn their parents.

Roberts just elides the fact that historically, an even higher percentage of poor and middle class people would out earn their parents.

So his statistics are not wrong, he just presents them in a certain light.

Interesting. I'll have to fully grok it later. I've never thought about defining upward mobility as doing better than your parents.

I feel like there has to be a better way to portray class mobility than statistics like % out earning parents. It seems that (im not an economist) out earning parents is crude because it doesn’t take actually moving classes into consideration. Can one not out earn their parents and still be poor or have not moved classes?