The battle of the tax returns begins Friday, with President Obama and Vice President Joe Biden releasing theirs to the public and urging Mitt Romney to join them. The Obamas revealed that they earned a combined income of $789,674 in 2011, of which they paid 20.5 percent in federal taxes—a total of $162,074. Their income took a big dip from last year, when they reported about $1.7 million. (About half of this year's total comes from book sales, with the other half being the president's salary.) The Bidens, meanwhile, reported taking in $379,035 last year and paying $87,900 in federal tax—an effective tax rate of about 23 percent.