If someone asks why there is a graduated tax rate, the answer is: diminishing marginal utility. In less technical terms, the more of a thing you have, the less each single one is able to impact your life. If you have one chocolate cake, it's a great day! If you have 6,000 chocolate cakes, your day is not 6,000 times better. Someone making $20k is impacted more by a 19% tax in terms of the minimum bills they need to pay for food and shelter than someone making $200k. From the book The Wealth of Nations, the poor spend their money on the basic needs of life, while the wealthy can spend money on luxuries. Because of that, it is not unreasonable to impose a higher rate on the wealthy; if taxes are a necessary evil to fund the Federal Gov't (see the collapse of the articles of confederation for why), then the poor are the ones most impacted by that tax. 19% may represent the same percentage of overall income in a flat tax system, but it is regressive with regards to the lower income bracket's ability to buy food and pay rent.