Even before the recent tax cuts, incomes were growing fastest at the top of the income scale.  Beginning with Reagan, the series of Republican tax cuts has over-whelmingly benefitted the rich.

“An April 2004 CBO study showed that between 1979 and 2001 (the last year CBO examined), the average after-tax income of the top one percent of households rose by 139 percent ($409,000) after adjusting for inflation, compared to a 17-percent ($6,300) increase for the middle fifth of households and an 8-percent ($1,100) increase for the bottom fifth.” Full Story.

The magnitude of the income tax cuts and the change in tax rates under the Reagan-Bush-Bush regimes is important but there is more to the story.  It’s also important to look at what  taxes have already been cut:  capital gains tax rates; taxes on dividend income; repeal of the estate tax in 2010; increased business depreciation schedules etc.  Each of these changes favors those with investment income over those with labor income, thus magnifying the effect of the reduction of income tax rates.