The original article was not based on incomes in any age ranges either. If they had wanted to do a more rigorous analysis, they would have compared say, 18-34 y

The original article was not based on incomes in any age ranges either. If they had wanted to do a more rigorous analysis, they would have compared say, 18-34 year olds in 1970 and today. Anyway, the point is the first half of the article is fundamentally mistaken, There are ways to do more interesting analyses, but this one was mostly incoherent.