The logical failing of the last statement is that is suggests a finite amount of wealth - of which the super rich are getting at the expense of everybody else. In truth EVERY bracket has, in fact, increased its income, in real dollars, over the period represented (with caveats as do ented in this thread - no one has responded to my very poignant post about 401K accounts that began in EXACTLY the same year as the OP's data). Meaning, necessarily, wealth is not finite at all, and there need not be RE distribution of wealth for one group to benefit more than another; and it ONLY stands to reason that, regardless of system, that the top 1% will ALWAYS be accelerating beyond the mean, because that is what making them the top 1%! What would be interesting, would be to delineate the top 1% in 1979 - and graph those specific PERSONS from then forward.
For instance, if I made $100,000 one year, while my wife made $50,000 - the top 50% would have made 2X what the bottom 50% made. Then, I lose my job in July, after earning 50K, but my wife patents a new vaccine she's been working on, and makes 500K - THEN the top 50% is earning 10 times the bottom, increased its income 5X, while the bottom 50% stayed the same ! Doesn't tell the story very well, does it.