Earlier quoted context omitted.
> This is almost a natural law of wealth. The article is about how the post-1975 period differs from the pre-1975 period. So it's demonstrably not a natural law. Natural laws don't change over time.
From 1960 to 1985 the top marginal tax rate crashed from 90% to 30%. And then of course there's the demise of private sector unions, the effects of computerization, etc. Arguably, it was always a natural law, but the 1970s were an inflection point after which capital was allowed to accrue advantages at a much faster rate.
Nobody paid 90%. The tax rate reduction was countered with the closing of loopholes. (There are still a lot.)
Evidence for this is the nearly constant fraction of GDP collected in taxes. The other points are correct. Also, real incomes have both increased at the top end and shifted up for the population.