You want maximize collected tax, fairness & equity, and incentives. This means: 1. convex effective tax curve when income increases. 2. curve is progressive

You want maximize collected tax, fairness & equity, and incentives. This means: 1. convex effective tax curve when income increases. 2. curve is progressive (increasing) to adjust for diminishing marginal utility of income and wealth. https://www.investopedia.com/ask/answers/072815/what-marginal-utility-income.asp https://www.investopedia.com/ask/answers/072815/what-margina... The emphasis on effective. Meaning: (income - taxes + benefits) curve is smooth and no tax avoidance. Incentives for the poor, the middle and and the rich. Then you fight over what level the is (political question). Big tax jumps (suggested by the left) or linear tax (suggested by right) don't hack it.