As economist Russ Roberts often points out in these inequality discussions, the quintiles that are used to show growth only in the upper class does not refer to the same people over time. When you follow people over time, they generally move up into higher quintiles thus "getting richer."
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.
I'm concerned about the drop in mobility too. But stepping back for a bit, imagine mobility stayed the same, what would that mean? Would that mean everyone earns roughly the same after a few generations? Or would it mean the income inequality pyramid gets flipped upside down? Is that even feasible?
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?
Wouldn't you expect that to be a one-off change that exhausted itself within a decade? And then a return to old income growth rates?
Like, middle class income growth has been stagnant for several decades now despite steadily increasing productivity, how can you explain that whole period using demographic shifts around 1972?
https://russroberts.medium.com/do-the-rich-capture-all-the-g...
He also talks about "what happened in 1972" is more about demographic shifts due to divorce, single parent homes, and children leaving home sooner:
https://cafehayek.com/2013/11/inequality-in-two-graphs.html