The reality is much more boring. Thanks to "math," they've determined that if the ratio of incomes from 1945-1974 held steady, the bottom 90% would have "more" than they do now. Of course the bottom 90% itself is a fantasy and you can find yourself in or out of it many times in the course of a career.
But is it possible that maybe, just maybe, wealth distribution isn't a 0 sum game? And maybe being in the bottom 90% is better now than it was 40 years ago, because of, I don't know, iPhones, next-day delivery for anything you want, telehealth, instant access to the world's information, electric cars, and many other things that 1 percenters have made for us?