Wealthy people dont pay income very much at all, their income is made via capital gains. Also consumption based taxes are the primary thing that this would be so the richer you are the less this will be as a percent of your income.
Capital gains are profits from the sale of assets such as stocks, bonds, real estate, and antiques. Nine states (Arizona, Arkansas, Hawaiʻi, Montana, New Mexico, North Dakota, South Carolina, Vermont, and Wisconsin) provide income tax deductions or preferential rates for all long-term capital gains income. Other states—such as Connecticut, Idaho, Kansas, Kentucky, Louisiana, Maine, Maryland, Mississippi, Nebraska, New Jersey, North Carolina, and Oklahoma—offer tax reductions for realized gains from certain assets located solely within state boundaries.[11] These tax subsidies disproportionately benefit high-income and high-wealth families and tend to worsen economic inequality across both economic and racial dimensions.
Oh man, if only the authors of the study had thought about capital gains taxes, then maybe the map above that's only using income to divide the population would have been better somehow.
Capital gains isn't a "2nd tax on money people already earned". If I put my money in a bank account and earn 10% interest (laughable I know) and I earn $10k on the $100k I have in the bank, I pay income taxes on the $10k. If I buy a piece of land for $100k and I sell it for $110k, I pay capital gains tax on the $10k. In both cases I didn't work for the money and I only paid taxes on the profit.
Capital gains tax is NOT taxing money twice, and even if it was, sales tax is a much more direct "taxed twice" tax. There is no such rule as "money can't be taxes twice" in our society. Capital gains tax should be done away with and all profit should just be called "income" and taxed accordingly, just like the rest of us who work for a living.