Women make up roughly half the workforce. But in 2015, female full-time, year-round workers made only 80 cents for every dollar earned by men, a gender wage gap of 20%, according to the non-profit Institute for Women’s Policy Research (IWPR).

If change continues at the current pace, IWPR predicts it will take until 2059 for women to reach pay parity — and for women of color, the rate of change is even slower.

Tuesday is Equal Pay Day, a symbolic day for advocates in the U.S. to show support for women in the workforce and draw attention to the gender pay gap.

Here’s what you need to know about Equal Pay Day:

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