The couple's wealth since Bill Clinton's presidency ended in early 2001 has been generated largely from paid speeches, lucrative book deals and successful investments.
Some of that wealth has been detailed over the years in the financial disclosure forms Hillary Clinton was required to file as a senator and as secretary of state, as well as in tax returns she released as part of her 2008 presidential run. These forms record income from both Clintons jointly.
But loose federal disclosure rules, requiring that officials report the value of their holdings using only wide ranges, leave much room for interpretation. And while Hillary Clinton's past tax returns offer more data points than exist for most other potential presidential candidates, the information is incomplete - and out of date.
In 2010, then-Secretary Clinton's financial disclosures revealed a net worth totaling between roughly $10 and $50 million. In 2012, the last year for which she disclosed finances, Clinton's net worth was estimated to be between $5 million and $25 million.
Clinton deflected a question about her net worth during an interview with Fusion's Jorge Ramos that aired Tuesday night. Asked if she knew the figure, Clinton replied, "Within a range, yeah. I mean, we have two very nice houses, which we're very proud of and not selling anytime soon." When Ramos asked if it was millions, she said, "Yes indeed."
A spokesman for Clinton did not respond to requests for comment or to specific e-mail questions about her net worth.
Lawyers and government ethics officials say federal personal financial disclosure rules are vague for a reason. The rules are designed to prevent conflicts of interest between those in office and their investments, not to provide values for specific holdings.
Assets such as mutual funds and stocks, and liabilities like credit card debt must be disclosed by name if their worth exceeds a certain amount.
"These governmental personal financial disclosure forms are not intended to represent either in general or specifically net worth," said Jan Baran, a partner at law firm Wiley Rein with experience in government ethics law.
In 2010 for example, Clinton disclosed two JP Morgan accounts each worth between $5 million and $25 million. Her 2011 and 2012 disclosures show only one JP Morgan account worth between $5 million and $25 million. It's unknown whether Clinton's net worth during this period actually decreased, or if assets were simply consolidated into one account that remained within the $5 million to $25 million range.
Also unclear is how the Clintons' income factored into their reported net worth. The tax returns Hillary Clinton released during her 2008 campaign show that the Clintons made $87.3 million in joint adjusted gross income between 2001 and 2006. Full tax returns for years beyond 2006 have not been made public, but a recent Washington Post report on Bill Clinton's paid speeches shows $49.2 million in further earnings from appearances alone between 2007 and 2012. Adding those figures together shows that the Clintons' confirmed income between 2001 and 2012 was at least $136.5 million.
The result is that Americans knew relatively little about Clinton's total wealth while in office - and probably know even less now, as there are no publicly available documents showing income or net worth for the period since she left the State Department.
That said, it's clear that both Clintons have been paid handsomely during that time, from continued speeches and for Hillary Clinton's recently released book.
Some have attempted to estimate the extent of the couple's recent financial fortunes. Bloomberg News reported, for example, that Clinton "earned at least $12 million in 16 months since leaving the State Department,” though the report acknowledged that the information was based on incomplete estimates.
The lack of specific information has led to uncertainty among Clinton's rivals and backers, all of whom would like to know
to what degree her personal wealth might play a role in an election in which populism and income inequality seem likely to be factors. After all, Democrats were successful in using Mitt Romney's riches against him in 2012. Romney's net worth was reported to be about $250 million.
"It's hard really to come up with much more specifics than what [the documents] give," said Tim Miller, who as executive director of America Rising PAC, a Republican opposition research group, is in charge of helping to shape GOP attacks on Clinton.
If Clinton decides to run for president, she would have to file another financial disclosure form - and she would almost certainly be pressured to release more up-to-date tax returns.
Only then will anyone know how rich she really is.