[dragonwriter]

> Extremely progressive taxation isn't effective.

It pretty clearly is, which is why each downward shift of the nominal tax burden in the US (stretching back to the income to payroll tax burden shift under Reagan) has had noticeable effects on accelerating inequality.

> The very rich have ways of hiding or deferring income.

Mostly, as a direct result of tax policy directly designed to frustrate tax progressivity, most notably giving preferentially low tax rates to kinds of income mostly earned by the rich (long term capital gains are a big example), and loading up extra taxes (on top of normal income taxes) on labor income.

Making taxes more progressive is less about increasing progressivity in nominal rates as it is about addressing those issues (though making the nominal rates more progressive may also be part of it.)