The most recent report from the Congressional Budget Office on Effective Federal Tax Rates is based on statistics from 2005. I found the report very enlightening.
Of the total individual income taxes collected that year, 99.4% were paid by the highest earning 40% of American households. That means 60% of the population paid less than 1% of the total taxes.
The lower 40% of households, on average, got more money back (through tax credits, EIC, etc.) than they paid in. This segment included people earning up to $48,000 per year.
The top 20% of earners paid 86.7% of the total taxes collected, with the top 10% shouldering 72.7% of the total tax burden for the entire country.
Given this objective historical data, would somebody please explain to me the theory that the rich are undertaxed?