The plan would require all companies with 100 or more employees to earn “equal pay certification” by proving they pay men and women the same for doing work of the same value, or else be fined 1% of their profits for every 1% wage gap. It would also force corporations to report the share of women in leadership positions, bar them from asking about prior salary history, and prohibit them from using forced arbitration to handle pay discrimination claims.

Harris has deemed her plan a “first-ever national priority on closing that pay gap,” but it does have some close peers. It is similar to an Obama-era rule that required employers of 100-plus workers to report pay data by race and gender. (You might recall that the Trump administration tried to revoke the rule for being too “burdensome” to business, but a judge rejected that rationale in March—a ruling the administration is now appealing.) But Harris’s plan adds a punitive layer in the form of the fine, introducing what could be a powerful stick to the equation. That aligns her proposal with initiatives passed in Iceland and France, where gender pay gap reporting is accompanied by financial penalties. And that contrasts her idea with the approach taken in the U.K., where firms don’t face fines for the gender pay gaps they report; the idea being that naming and shaming is enough of a motivator.

Harris is already playing up the threat her plan imposes. At a rally on Sunday that previewed Monday’s announcement, she said her measure will hold “corporations accountable for transparency and closing that gap.”

“There will be penalties if they don’t,” she said to applause.

The fine certainly adds teeth to the initiative—plus it’s a revenue stream. Her campaign estimates it will generate $180 billion in its first decade, which will, in turn, help fund a paid family and medical leave plan that Sen. Kirsten Gillibrand has introduced and Harris has backed. But at the same time, the fine is, essentially, a new tax on business, which means implementing the plan in its entirety would require Congressional support.

That’s important since the proposal is likely to face opposition from Republicans. “We don’t need to strap new regulations, burdens or fines on businesses to create opportunities for women, and President Trump’s economic record is a testament to that,” a spokeswoman for the Republican National Committee said in response to the idea.

But on her side Harris has that pesky 20% pay gap, which is even worse for black and Latina women, and research that says that when companies are required to disclose their pay data their gender gaps shrink.

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