Mitt Romney's tax returns and the tax rate he paid on his income have been hot issues in the recent Republican primaries.
"What's the effective rate that I've been paying? It's probably closer to the 15 percent rate than anything because my last 10 years, my income comes overwhelmingly from investments," he recently told reporters.
So why does a multimillionaire pay just 15 percent on his income? After all, the top income tax rate is 35 percent and many middle-class people pay over 20 percent.