The Coming Tax Hike
Going back to the tax rates of the 1990s doesn't mean that households will pay 1990s taxes. Because the tax brackets haven't risen along with incomes, average taxes would be significantly higher, and grow each year.
If the [Bush] tax cuts expire, income-tax revenues by 2018 will rise to 10.8% of the total economy from 8.7% today – an increase of 24%. Compared to the average over the last 50 years, allowing the rates to rise would increase tax revenues by 32%.
Believe it or not, income taxes will rise even if the tax cuts remain in place, because the revenue-increasing effects of bracket creep more than offset the lower rates. With the lower rates, total income-tax revenues will increase to 9.3% of GDP by 2018. This level is 7% higher than today, and 13% above the 1957-2007 average....
So even if the tax cuts are made permanent, future Americans will pay a greater share of their incomes to the government than in the past.