Much has been made of the current presidential candidates' tax rates--and their hesitance to release their returns. Of the apparent frontrunners for their respective parties' nominations, Mitt Romney has attracted the most attention.

While the candidates, because of their relatively large salaries, pay a relatively large dollar amount in income taxes, the tax controversy stems from the fact that the Romneys' effective tax rate is relatively low compared to most Americans.

President and Mrs. Obama paid a tax rate of roughly 26 percent on their income of $1.7 million. For Newt and Callista Gingrich, the comparable figures were 32 percent on income of $3.1 million. For Mitt and Ann Romney, however, the numbers are much more dramatic. While the couple's income was several times more than the other two candidates' combined, around $21 million, they paid only about 14 percent of that in income tax.

That figure is quite favorable compared with relatively wealthy U.S. households. For example, a household at the 90th percentile of income as of 2007--representing income of roughly $100,000--paid about 18 percent in taxes, and those wealthier, in the top 1 percent, paid roughly 21 percent.

How, then, are the Romneys able to pay less in taxes, on a percentage basis, than the Obamas and Gingriches, despite making considerably more money? According to The New York Times, Mitt Romney's income is almost all from investments, rather than salary, which led to a different calculation than was used for the other candidates. The Romneys also donated nearly $3 million to charity, more than 10 times what the Obamas donated and more than 30 times what the Gingriches donated.

Source: The New York Times, "Putting Candidates' Tax Rates in Perspective," David Leonhardt, Jan. 24, 2012