Heidi M. Przybyla

USA TODAY

Hillary Clinton released her 2015 tax return Friday, as her campaign dials up the pressure on Republican Donald Trump to do the same.

Clinton, who filed jointly with her husband, paid an effective federal income tax rate of 34.2% last year, and the Clintons donated 9.8% of their adjusted gross income to charity, according to the campaign.

The Clintons took in $10.6 million in income in 2015, a majority of which came from paid speeches by Bill Clinton, while $3 million came from book royalties.

Their 2015 income was a little more than a third of what it was the year before and about half of their haul in 2007, the last full year in which Hillary Clinton was running for president. Including state and local taxes, the pair paid an effective rate of 43.2% in taxes 2015.

Sen. Tim Kaine, Clinton’s running mate, and his wife, Anne Holton, are also releasing 10 years of their returns showing they earned a combined $313,441 and paid a 25.6% rate, taking into account federal, state and local taxes.

Trump has repeatedly rebuffed calls to release his most recent tax returns because they are under federal audit. Yet he's also refused to release prior returns that would provide information about his income, foreign holdings as well as charitable giving.

“Hillary Clinton and Tim Kaine continue to set the standard for financial transparency as she releases her 2015 personal tax return and builds on the Clintons' tradition of making their returns public since 1977,” Jennifer Palmieri, communications director for the Clinton campaign, said in a statement.

“In stark contrast, Donald Trump is hiding behind fake excuses and backtracking on his previous promises to release his tax returns," Palmieri added. "He has failed to provide the public with the most basic financial information disclosed by every major candidate in the last 40 years. What is he trying to hide?”

Trump has said “there’s nothing to learn” from his returns, and he has released a personal financial statement, which is legally required.

His campaign has said his net worth is in excess of $10 billion. Every major party nominee since the late 1970s has released tax returns before Election Day.

A year ago, Clinton released past years' returns, which showed the couple earned just over $28 million in 2014 and $27 million in 2013, more than double the $13 million they earned in 2010 when she was still serving as secretary of State.

The Clintons earned $21 million in 2007, as Hillary Clinton, then a U.S. senator, was running for president. Bill Clinton earned $10 million from speeches and $4 million in book sales that year, but their combined income dropped to $5.5 million in 2008.

The release coincides with a new Clinton campaign web video featuring Republicans pressuring their nominee to release his returns.

The video includes 2012 Republican nominee Mitt Romney, Senate Majority Leader Mitch McConnell and Texas Sen. Ted Cruz, Trump's primary rival.

“We will only really know if he’s a real deal or a phony if he releases his tax returns,” Romney says, suggesting that maybe Trump isn’t as rich as he claims, hasn’t paid the tax rate Americans would expect him to or hasn’t donated to veterans and other charities as he's said he has.

“For the last 30 or 40 years, every candidate for president has released their tax returns, and I think Donald Trump should, as well,” McConnell says.

“He doesn’t want to do it because presumably there’s something in there that is bad,” Cruz says.

Late Friday afternoon, the Trump campaign issued a response to the Clinton tax release.

"Hillary Clinton has turned over the only records nobody wants to see from her," Trump spokesman Jason Miller said in a statement. "Hillary Clinton is at the center of an international corruption scandal that reveals her use of government authority and influence for personal gain. The records we need to see are those being hidden, deleted, obstructed and stashed away by Hillary Clinton to keep authorities from untangling this corrupt scheme that reaches into the world's shady corridors of power. Everything she doesn't want us to see has been digitally shredded or put under lock and key."