President Clinton listens to former Secretary of State Hillary Rodham Clinton speak at a student conference at Arizona State University on March 22, 2014. (AP/Matt York)

Bill Clinton received some criticism this week for his defense of the paid speeches he gave after leaving the White House. "I got to pay our bills," the former president told NBC's Cynthia McFadden, adding that he had taken "almost no capital gains" in the past 15 years.

That statement was not entirely accurate. Clinton and his wife, Hillary Rodham Clinton, did enjoy returns on their investments at first, according to tax returns she released during her first campaign for the office her husband held.

Since 2007, however, their wealth has earned them almost nothing, and they probably have not taken significant capital gains, according to a review of Hillary Clinton's financial disclosures from her time as secretary of state.

The Clintons' portfolio has performed poorly because it is almost entirely in cash. As of 2012, when Hillary Clinton left the State Department, the couple's wealth was in an account at JPMorgan likely worth between $10 million and $25 million.

Just like everyday Americans, the Clintons keep their money in a regular old savings account. The former president pays the bills with money he earns by working, not from dividends and interest.

It's just that for most American dads nearing retirement, their jobs haven't paid quite as well as Bill Clinton's most recent speechmaking gig.

In a global economy with an increasingly unequal distribution of wealth, the Clintons' massive savings account is unusual. People as rich as they are typically put their money to work in hedge funds, bonds, real estate or just about anything else that's profitable, rather than keeping it in cash.

Not all the wealthy are politicians, though. The Clintons' financial strategy is a response to the intense scrutiny placed on them throughout their career in American public life --and a reminder, in dollars, of how much they've been willing to give up to achieve their ambitions.

When Bill Clinton became president, the couple assigned their money to a blind trust, managed by an independent adviser who made decisions without their knowledge or instructions to avoid conflicts of interest. They didn't have much at the time, and eight years later, they left the White House in debt. The former president did have bills he had to pay -- legals bills resulting from his tumultuous tenure in the Oval Office.

Bill Clinton began giving speeches around the world, collecting a cool six figures with most of his appearances. Soon the adviser of the trust had some real money to invest.

The Clintons continued to hold their wealth in trust until Hillary Clinton's first presidential campaign. Federal officials told them that their trust was out of date, and to comply with the rules on ethics, they would have to liquidate it.

The Clintons sold all of their assets and did not reinvest the proceeds. The income they would pass up by keeping the money in cash and U.S. Treasury bonds was a price they were willing to pay to shield Hillary Clinton from any questions about conflicts of interest.

Others of similar stature have also changed their investment strategies. President Obama and First Lady Michelle Obama hold less than $5 million in Treasury bonds and several hundred thousand dollars in index funds, according to their most recent financial disclosure.

The Clintons' finances are unusual even among politicians in that as of 2012, almost all their money was in cash, and they had a lot of it.

In 2008, they kept the money at Citibank, mostly in Treasuries. They moved the money into Treasuries and cash at JPMorgan in 2009, when it was worth at least $10 million. (On the federal disclosure forms, the values of assets are reported in ranges.)

By 2011, all the money -- less than $25 million -- was in cash.

The 2012 disclosure states that the Clintons earned between $50,000 and $100,000 in interest on the account, a rate of between 0.2 percent and 1 percent.

Bill Clinton earned more in royalties on his books. His book about the economy, "Back to Work," brought him between $100,000 and $1 million that year. "My Life," the autobiography he published in 2004, added another $50,000 to $100,000. His speeches, by far, were his largest source of income. His wife's memoir, "Hard Choices," was published after she left the State Department, and it is not known how much the book is generating in royalties.

There are still other questions about the Clintons' money. If the former senator and first lady had simply wanted to avoid questions about her finances on the campaign trail, it isn't obvious why she and her husband didn't simply invest in index funds, as the Obamas have done.

After deciding to keep the money in cash, though, the Clintons then apparently ignored the federal limit on deposit insurance. The government insures a joint account owned by two people for up to $500,000. They might have deposited the money at several banks, in case JPMorgan were to fail. President George W. Bush, for example, kept some of his money in certificates of deposit at a number of banks.

Whatever their reasons, the irony is that Bill Clinton's speeches have generated as much controversy as any investments the couple might have made.

A number of those who have paid him to speak have also donated money to the couple's charity, the Clinton Foundation. News media and a new book by the conservative author Peter Schweizer have scrutinized whether contributions to the charity created conflicts of interest while Hillary Clinton was in office.