26 days ago
@futurebird @ligasser @mattdm @unchartedworlds
This is a good example for Calculus courses. The tax brackets define the marginal tax rate, which is a step function (as a function of income). The tax you pay is the integral of this function, which is a continuous piecewise-linear function. Subtract the tax function from the identity function to get your net after-tax income function. Theorem: this is an increasing function if and only if the marginal tax rate is always less than 100%.