> so advocating for 'sane progressive taxation' is just a nebulous cop-out that doesn't provide anything concrete enough to be discussed or analyzed.
Capital gains is merged into one income tax bracket. All money earned in a year is one single income. Income from 0 to your providential happiness threshold according to heuristic analysis based off the methodology used in this study: https://www.princeton.edu/~deaton/downloads/deaton_kahneman_...
From that point to 100x the happiness threshold you curve progressive taxation from 0% to 90% quadratically, approximating the median around 25% at 50x. Your total tax burden is simply the area under the curve, so rather than having tax brackets you use actual math to make sense and tax progressively all income earned.
That means any money made over, if happiness is 75k, 7.5 million is 90% taxed forever. I'd even wager to make it 100% as a short term measure to help dramatically curb income inequality. Note this rate is actually 2% lower than the highest its ever been, but in practice capping capital gains would have a dramatically larger effect on economic planning.
Additionally, you need tariffs on exported wealth, on corporate holdings accounts, and on physical goods hoarded, on property all at progressive rates to avoid off-shore tax evasion, hiding your money in a business account, buying material goods to hide your wealth, and stop the current and tangential issue of land hoarding that would be an even bigger problem under a legitimate tax scheme.
Finally, you institute a 10 year wealth tax to try to reclaim some of the amassed ownership of the means of production the ultra-elite have racked up over the last decade and stop some of the rent seeking. It is not just about stopping them from acquiring even more of a share of ownership, its about getting some of it back. The rates here are not something I have researched much, but something of the sort may be required since so much of total wealth has moved to the top.
You would keep sales tax as a means to fund local and state government, because while regressive if you try to push progressive taxes locally you will just have regional wealth flight. I strongly disagree with the argument that if you tried realistically taxing the rich to pay for society that they would all flee internationally - because the tax burden is pretty close to this in almost all European countries. Where else are they going? Politically unstable and unsafe third world nations? China? Russia? You would absolutely want some global effort here to prevent there from being such an easy escape route, but its a problem of global scale after all, the asset controllers in the US also dominate international commerce and are as much a problem in their influence on every other nation as they are here.