A flat tax makes no sense. To be clear, there may be additional policies associated with a flat tax that may make a lot of sense. I'm talking purely about the

A flat tax makes no sense. To be clear, there may be additional policies associated with a flat tax that may make a lot of sense. I'm talking purely about the "flat percentage" bit. The only advantage it provides is a slightly less complicated calculation. But it simplifies a calculation that can be represented in a few lines of code and a single excel formula. As a trade off, it completely ignores the idea that the marginal value of money changes depending on the base. If you earn $50k another $10k has a lot more marginal value than if you're earning $500k. It sounds good but it's terrible policy.