This second graph (of six) compares the percent of income controlled by each income quintile with the percent of taxes paid. That is, the richest 20% of Americans received some 55% of the country's income and paid 70% of the tax receipts. The poorest 20% earn less than 5% it looks and pays almost nothing.
Different people will tend to put different weights on which of those statistics they are most concerned about. Personally, I'm more interested in why the third and fourth quintiles aren't paying a percent of tax receipts commensurate with their income (recognizing that I'm somewhere in the bottom of that group so it's not to my interest to point it out). While many Republicans - including our local candidate for Congress, Richard Hanna - correctly point out that a system where more than half of the people don't pay any income tax is unsustainable, I have yet to hear them officially say this implies tax rates should be raised on the middle class. But we haven't heard the Democrats propose that either.... Maybe the Greens will be so kind as to support some fiscal sustainability as well as environmental?
Hat tip: Mankiw
And, according to the CBO and Marron, tax revenue is expected to climb dramatically to an all-time high in the next couple decades unless policy changes or prolonged economic turmoil prevent it:
That rapid growth reflects six factors. First, the economy will recover, lifting revenues from currently depressed levels. Second, the 2001 and 2003 tax cuts will expire, as will tax cuts enacted in the 2009 stimulus. Third, the Alternative Minimum Tax, which is not indexed for inflation, will boost taxes for millions more taxpayers. Fourth, the new taxes that helped pay for the recent health legislation will go into effect. Fifth, retiring baby boomers will make more taxable withdrawals from tax-deferred retirement accounts. Finally, in a phenomenon known as bracket creep, growing incomes will push taxpayers into higher brackets and reduce their eligibility for various credits.
Together, those six factors will increase tax revenues by 8.4 percentage points of GDP over the next 25 years, according to CBO. ... The trillion-dollar question, however, is whether policymakers will allow them to happen.