FYI, your marginal tax rate is the rate you pay on the "last dollar" you earn; but when you view the taxes you paid as a percentage of your income, your effective tax rate is less than your marginal rate, especially after you take into account the deductions and exemptions, i.e. income that is not subject to any tax.

Tax Data: Married filing jointly, Capital Gains & Regular,Historical Corporate, Corporate Tax Schedule (page 16) pdf