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By Fortune.com/Ryan Kilpatrick
Updated Mar 09, 2017 @ 9:30 am
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While women’s rights activists marched worldwide to demand equal pay on Wednesday, Iceland celebrated International Women’s Day by becoming the first country in the world to require that businesses prove they offer equal pay to their employees.

The Nordic nation is the first to make this mandatory for both public and private firms, where wages are difficult to mandate, the Independent reports. The new law will require every company with 25 or more staff to obtain a certificate demonstrating that they pay all employees equally “regardless of gender, ethnicity, sexuality, or nationality.”

Thousands of Icelandic women left their workplaces at 2:38pm in October and joined a demonstrated outside parliament to protest the gender pay gap. According to unions and women’s groups, differences in pay with men mean that women in Iceland effectively work for free after that time each day.

Although the World Economic Forum has ranked Iceland top in the world for gender equality for eight years running, women in the small island nation still earn up to 18% less than men on average.

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Having already introduced a 40% quota for women on boards of companies with more than 50 staff, however, Reykjavík plans to make the pay gap a thing of Icelandic history by 2022.

This Story Originally Appeared On Fortune