I recently [asked this question](https://skeptics.stackexchange.com/q/50540/3943) about a statistic quoted by Kurt Andersen designed to illustrate the current wealth distribution in the USA in his book [Evil Geniuses](https://en.wikipedia.org/wiki/Evil_Geniuses:_The_Unmaking_of_America). It provoked a great deal of (unintended) discussion as I only wanted to check whether his illustration was correct.

But he makes many other claims in the book (which are more relevant to much of the unintended commentary).

He specifically claims that the US distribution of income and wealth has skewed spectacularly in favour of the rich in the last three or four decades. In his words (my highlighting):

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> Before 1980, all Americans’ incomes grew at the same basic rate as the overall economy. Since 1980, the only people whose incomes have increased at that rate are people with household incomes in the range today of $180,000 to $450,000. People with incomes higher than that, the top 1 percent, have gotten increases much bigger than overall economic growth. (*Meanwhile 90 percent of Americans have done worse than the economy overall.*)
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and

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> During the grand decades between World War II and 1980, when U.S. median household income more than doubled, 70 percent of all increases in Americans’ income went to the bottom 90 percent. *Since 1980, nobody’s income has doubled except for the richest 1 percent*, and the incomes of the entire nonrich 90 percent of Americans have gone up by only one-quarter.
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Are these claims accurate in describing how inequality has skewed in the US since 1980?