Thomas Piketty shows in his book, Capital in the 21st Century, that the wealth disparity we see today is the typical condition. What we saw post WWII through 1982 was anomalous.
I have said that the present disparity can be laid to virtual elimination of the progressive income tax structure in the 1980s combined with the compounding effect of continually taxing unearned income at a lower rate than earned. I have seen nothing to convince me otherwise.
Steve Forbes popularized the notion of flat tax, which would tax different dollars earned at the same rate. The idea is still around. This would of course completely eliminate the remaining vestiges of progressivity in the tax structure. I wonder if people realize how a flat tax would impact income equality. If you continued to tax unearned income at a lower rate, Forbes was never completely clear on his intentions, it would be dreadful for a consumer economy, I would think. In the U.S., the effect would be to shrink the middle class even more and grow the ranks of the impoverished.