The United States pays higher corporate taxes than most other G20 countries, but it's not as high as it looks at first glance. Companies often pay much lower than the rate that is written into law after taking into account deductions, credits and other provisions of the tax code.

Why this matters: One of the GOP's biggest arguments for lowering the corporate tax rate — now likely to go down from 35 to 21 percent in the final tax bill that's being written now — is that it will make the U.S. more competitive internationally. While economists disagree on whether the bill would effectively do this, it is true that rates in the U.S. are comparatively higher than in other countries.

What the different rates measure, per the Congressional Budget Office:

• Statutory rate: The legal tax rate. Federally, the top corporate rate is 35 percent, but with state taxes factored in, the total average rate was 39.1 percent in 2012.
• Average corporate rate: The total amount of corporate taxes a company pays as a share of its income.
• Effective marginal rate: A corporation's tax burden on returns from a marginal investment.