Wouldn't a completely flat tax with a fixed deduction/rebate achieve that? Say, 25% of your income minus $10k. The marginal rate is always 25%, the average rate

Wouldn't a completely flat tax with a fixed deduction/rebate achieve that? Say, 25% of your income minus $10k. The marginal rate is always 25%, the average rate is negative for incomes below $40k and asymptotically approaches 25% as it increases.