Tuesday is Black Women’s Equal Pay Day. Here’s what you should know about the gap.

The National Women’s Law Center notes that this gap can begin to widen over the course of a black woman’s career, causing her to lose nearly $870,000 in potential earnings to the wage gap. And in several states, the wage gap can be even bigger. In Louisiana, for example, black women make less than half of what white men make. The gap in black women’s pay is due to several factors. A 2014 report from the National Women’s Law Center notes that women comprise some two-thirds of workers making $10.10 an hour or less, and of that group nearly half are women of color. Black women were overrepresented in the low-wage workforce according to the NWLC, making up 10 percent of low-wage workers but only 6 percent of the overall workforce.