A very bad idea in my opinion. The wealthy are in love with the "Steve Forbes Flat Tax" and happily promote it on the basis of "fairness" and "simplicity". A flat tax is bad for the wealthy in the long run, however, though few recognize it.
During a brief period in the 1980s the U.S, compressed brackets and rates, by raising the rate in the lowest bracket and drastically lowering the rate in the top brackets and reducing the number of brackets to the point of having nearly a flat tax. This, following on the heels of the great moderation of the 1950s-1970s, marked the beginning of the great wealth redistribution from the lower middle class upward to the wealthy class. If you want more of this, than a completely flat tax is the way to go. Regardless of the amount of progressiveness built into the income tax, the wealthy will end up paying much more per individual in nominal terms for government. As the income tax rate is flattened, however, the wealthy, collectively, pay about as much for government as the middle class collectively do, while benefiting far more from government than the middle class. Under a flat tax nearly all the investment money is left with the wealthy class, and virtually none remains with the lower middle class. This is a regressive tax system that leaves very little opportunity for those in the lower middle class to move up the economic ladder.
