""Everybody knows" sexual harassment is "a big problem," but if we learn precisely how big—including how many billions of dollars it steals from the economy every year—it will be addressed a lot faster."

In fact, the revelations of the past three months are a kind of data. People's stories are qualitative data or, as Brene Brown has put it, "data with a soul."

And like all good data, the #MeToo stories have forced us to reckon with a problem right under our nose.

The next step is collecting the data we need to attack the problem. In terms of the economic costs of harassment, three unanswered questions present themselves immediately.

First: How much? Studies say that somewhere from 25 to 85 percent of women are sexually harassed at work. With a range that wide, what the data is telling you is that you need better data.

Second: How does it affect people's career choices? One recent study shows that about half of women in their late 20s who are harassed seek a new job within two years. Many of them go into fields with more women where they feel safer but are also paid less. We need more studies to know who leaves, who stays, and where they all end up.

Finally: How do these choices impact the economy? This is the hardest to pin down. What's the expense of retraining? The value of lost institutional knowledge? The cost of the innovation we lose when potentially millions of women are driven into jobs that are beneath their ambitions and their talent?

Of course, any data agenda must include issues of discrimination above and beyond the current remit of the #MeToo campaign, from the pay gap to the lack of women in STEM fields to social norms that say women's roles are in the home and supposedly "out of the economy."

Sexual harassment and gender inequality aren't just Western problems. They're global, and they restrict women's economic potential worldwide. The key questions will be different in different societies. For example, we need to know whether a woman in an agricultural society has secure rights over her land, feels safe working it alone, and gets a fair price for her crops.

In 2015, the United Nations identified 53 pieces of information the world needs to track to achieve global gender equality. The problem is, right now, we only have a decent baseline for 10 of the 53.

One of my favorite Chinese proverbs says, "The best time to plant a tree was 20 years ago. The second-best time is now."

To the thinkers and leaders and influencers at the World Economic Forum, I say: Don't let this second-best time pass us by. We have a chance to collect a wealth of data in a systematic way so women's lives are fully part of the conversation in places like Davos.

We should have had the data 20 years ago. We need it now, and you have the power to collect it.

Commentary by Melinda Gates, co-founder and co-chair of the Bill &Melinda Gates Foundation. Follow her on Twitter @melindagates.

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