>For much the 1900s the top income tax bracket in the US was over 80%,
Top tax is not the same as effective tax rate. For example, when Reagan lowered the top brack from 50% to 37% while also closing taxable shelters,the amount the rich paid actually went up.
The CBO has all this type of data.
>This is a result of social policy.
It's more the result of changes in the world economy. Computers have made skilled jobs vastly more productive, while unskilled like making burgers or painting exteriors have not seen anywhere near the gains.
And as the rest of the world is catching up quickly to first world quality of life, the advantage the poor in the US had on the world labor supply is much less.
>while on average wages have tracked inflation
Only for white men in the US (and most first world countries). Poor women and minorities have seen vast gains in income over the past 40 years in the first world. The rest of the world has seen a massive gain for the poor.
Remember, the poverty line in the US is about the top 15% of incomes worldwide. Our poor are quite rich by world or historical standards. You used to be able to check this at globalrichlist.com, but it's now down. I suspect you can find this info elsewhere.
As some easy evidence to check, poverty line for a household of three in the US is $21k (and that pre-tax transfer. Post transfer is about 40k). Here's per country median incomes.
https://worldpopulationreview.com/country-rankings/median-in...