The required tax rates would still be unbelievably high though. Way higher than any other developed nation (some of whom already have >50% tax rates).

Canada has a tax rate that tops out at 50% (mostly), the US caps out at 37%[1]. I think we'd all be better off if the tax brackets went a lot higher. Rich folks tend to have a lot of inactive money that's just sitting around doing nothing - we can put it to more productive uses.

1. Please note, these numbers are off of raw income tax - both Canada and the US have other employment related taxes that I'm not counting here (like payroll) since their proportional contribution is pretty minimal.

You aren't including state taxes.

I am for the Canadian ones - where I can easily count the provinces. I am indeed too lazy to do the math on how much each of the fifty states leverage in taxes but it looks like they tend to come out well below 50% (except for CA, which is fair). Specifically, CT caps out at 43%, NY is at 45%, CA is at 49% and TX is 37% - since there are 0% state income states I find it reasonable to assume that rich people concerned with income taxes will chose to live in one of those 0% income tax states.

and payroll taxes of 12% on first $140k.