> You only need one statistic to understand America today, that working class Americans without college degrees have had their purchasing power stagnate since the 1970s(https://www.epi.org/publication/charting-wage-stagnation/)

Having a college degree was a much more selective measure in 1970 (about 10% of the population) than today (almost 40%). Consider a large law firm. In 1970, the only 4-year degree holders would have been the attorneys. A lot of work would have been done by well-compensated paralegals with high school diplomas. Today, everyone down to the receptionist will have a degree and the non-degree holders would basically be the maintenance and cafeteria staff.

So using your math, the income of non-college workers at the law firm could be stagnant from 1970 to today, even if the income of each specific position had increased significantly.