Now, it might also be accurate to state that the tax brackets need to be better adapted to suit the lower- and middle- class, featuring a more gradual climb over the lower incomes, rising up more slightly once the individual breaks 100K - making a model to illustrate this would be trivial, though I admit I don't care about doing such at this time. Also keep in mind that no one is really going to ever be satisfied with what the tax brackets settle upon, anyway.
However, commerce, trade, and industry are really what fuels an economy - income is made to be spent. When the companies benefitting from the spending aren't putting back into the system, you've got a major bust moving into the system. It's just a matter of time.