Also, this seems to ignore a major problem with how progressive income tax rates are figured in the US. You can work for years at a startup at a depressed wage

Also, this seems to ignore a major problem with how progressive income tax rates are figured in the US. You can work for years at a startup at a depressed wage, then have a windfall that makes up for it on average. That windfall (in California) will be taxed at a marginal rate of 52%. The only people that ever pay nearly that much are middle class. Some sort of time averaging would help. Anyway, the US tax code is complicated. Personally, I’d prefer a flat tax with universal basic income. This could replace income, capital gains and inheritance taxes in their entirety. (Along with a lot of social services bureaucracy).