How Unequal is the United States?

I see that the Congressional Budget Office has updated its sexiest data set: The Distribution of Federal Taxes and Household Income. The CBO data is always three years behind -- the 2009 update brings it up through 2006 -- and the current crisis will no doubt shift the landscape of American income. But the data set is still the best look at equality and redistribution in the country. Inequality and progressivity are in the eye of the beholder, but here are a few highlights:

--The 2006 average effective federal tax rate is 20.7%. In 1979 (the year the data set starts) it was 22.2%. The 2006 average rate for the bottom quintile of households is 4.3%; for the highest quintile it's 25.8%. In 1979 it was 8% and 27.5%, respectively.

--The 2006 average effective rate for the top 1% of households is 31.2%. It fell slightly since 2005, when it was 31.6%. In 1979 it was 37%.

--The bottom quintile of households pay 0.8% of all federal tax liabilities. The top quintile pays 69.35.

--The average pretax income for the bottom quintile is $17,200. For the top quintile it's $248,400. After-tax, it's $16,500 and $184,400.

--Inequality increased slightly between 2005 and 2006. In 2005 the bottom quintile had 4.8% of the total pie; the top quintile had 51.5%. In 2006 it was 4.7% and 52.1%, respectively.

A PDF of the whole dataset is here.