Mitt Romney is under fire for his lucrative time at Bain and his low tax rate, but all of his rivals are far wealthier than the average American.

There are no paupers among the Republican presidential candidates -- just varying degrees of what many voters would consider immense wealth.

Texas Gov. Rick Perry, perhaps the "poorest" among the lot, reported just $217,447 in adjusted gross income on his 2010 tax returns, of which he paid $51,000 in federal income taxes. His tax rate is not readily extrapolated from the two numbers because he claims exemptions for charitable donations, and he also earned income from investments, all of which would affect his bottom-line rate.

Perry's income pales in comparison to former Massachusetts governor and investment banker Mitt Romney, who made roughly $374,327 in speaking fees alone last year -- an amount Romney described Tuesday as "not very much" money. Maybe not for him, but it is for the average American, whose median income for 2010 was $49,445, according to the Census Bureau.

So far, Perry remains the only presidential candidate to release his tax returns, a ritual he does annually as governor. Following political pressure and jabs during Monday night's candidates' debate, Romney vowed to release his own returns for 2011 in time for April's tax-filing season.

Now, all of the candidates are coming under pressure to release of their tax returns. Former House Speaker Newt Gingrich said on Wednesday that he pays a rate of about 31 percent on his income, although he said he didn't know how much he earned annually as a business consultant in Washington since leaving Congress in 1998. The mystery should be resolved at least in part on Thursday, the day that Gingrich has promised to release his 2010 tax return.