Only 5% of Fortune 500 CEOs are women. Less than 2% of women get venture capital to fund their ideas. And women don't even make up 50% of Congress.
"It will be at least 60 years, at this rate, until we have equality," she said. "To me, equality matters. It can't wait."
There is hard work ahead, but Gates is pleased to have the work of the book behind her.
"Anytime you're vulnerable, it's difficult," she said of the more personal passages. "But I chose to be because I thought that people could relate more to me and the stories of the other women in this book."
She also wanted to show that her marriage, "like any healthy marriage," has tension at times. But being able to wrestle with things is how you move forward.
"I have gone into several situations where people kind of allude to, 'Well, it must all be fine for you because you've got a lot of money,'" she said. "No! It's not all fine. Sometimes this stuff just needs to be worked through. I get asked so often -- particularly early in the foundation's years -- 'How in the heck do you work with your husband?'
"Well, you just have to work it out, you know? If you believe in equality, you have to believe in it in your home, in your community and in your workplace," she said. "It's what holds us to our better selves."