Who Pays When "The Rich" Are Taxed?

Paul Waldmann produces a very interesting chart which illustrates that not only have the top marginal headline tax rates declined over time, the :

This is a difficult to justify response to a world in which there's more dispersion of incomes at the very high end than their used to be. More tax brackets would be a welcome development. Indeed, thanks to the widespread available of computers these days it should be possible to entirely dispense with the idea of "brackets" and express the rate as a continuous function of taxable income or consumption or whatever it is you want to use as the tax base.