A flat purchase tax is a horrible -blam!-ing idea. Workers living month to month spend the vast majority of their income on non-appreciating consumer goods, so they would be taxed on pretty much all of their income. The ultra wealthy spend very little of their income on consumer goods and so would be taxed on practically none of their income. The effective tax rate on the poor and middle class would be much higher than on the rich. Wealth and income inequality would grow substantially, and it's already bad in the current system.