Melinda Gates said they tended to avoid hashing out their disagreements in front of bigger groups at the foundation, saving them for private discussions, which they have on walks.
Bill added that he realizes critics of the foundation's charitable work don't often voice their concerns due to fears that they will lose funding.
When asked if the national reckoning over sexual harassment had affected her investments through Pivotal, Melinda Gates said that it hadn't so far, but that it had encouraged her to use her voice to encourage more women to speak out.
The 13-page letter from Bill and Melinda, out today, begins with a defense of their optimistic outlook that the world is getting better, while some might argue that growing climate change, massive refugee crises and uncertainty around the Trump administration suggest otherwise.
In terms of education, the Gates Foundation primarily targets high school-related endeavors and also supports early learning and postsecondary education. USA education initiatives are a distant second funding priority for the foundation, but the $450 million the Gateses spend annually on the issue makes them the top funders of schools reform in America.
Other top 10 questions include why the foundation gives money to for-profit corporations, why they don't donate more to US causes, if saving kids' lives fuels overpopulation and if the couple ever disagrees.
That's why the pair made a decision to deviate from the usual format of their annual letter this year; instead of talking about their friendship with fellow billionaire Warren Buffet, the Gates addressed 10 of the toughest questions they've been asked over their careers.
Trump has said he's a counterpuncher who goes after people when they go after him, only 10 times harder.
"No. It's not fair that we have so much wealth when billions of others have so little", Bill Gates answered. "The answer is that we think there's always going to be a unique role for foundations", he writes.
One of the questions in the letter is about what happens when the two of them disagree.
According to Melinda Gates, "We do the work because it's our life".
"We are partners in both senses that people use the word these days: at home and at work". "And they make Americans more secure by making poor countries more stable and stopping disease outbreaks before they become pandemics", Bill Gates said. "Did they scale and change the system for low-income and minority kids writ large, at scale?' And the answer when we looked at it, it was no", Melinda Gates said. We think that's a basic responsibility of anyone with a lot of money.
While jokingly saying the pair never disagrees, Melinda explained she gets the question "all the time", whereas Bill rarely does. Gates was the richest man in the world for 17 years.
Christopher Lubienski, an education policy expert who studies philanthropy, said he found the couple's honesty refreshing but noted their foundation's overall approach means it will continue to systematically influence education reform. But now it's impossible to imagine.