Serena Williams has called on black women to demand equal pay, in a blistering personal essay highlighting the combined race and gender pay gap.

In the piece, published by Fortune, the tennis star says that black women in the US make 63 cents for every dollar a man makes. As a result, women of colour “have to work – on average – eight months longer to earn the same as their male counterparts do in one year”.

Williams also calls attention the wage disparity that exists between black women and white women, stating that black women in the US earn 17% less than their white female counterparts.

31 July was Black Women’s Equal Pay Day in the US, and saw support from high-profile women including musician and actress Janelle Monáe, film director Ava DuVernay, California senator Kamala Harris and Insecure star Issa Rae. Sheryl Sandberg and Chelsea Clinton have also spoken out in support of the initiative.

In her essay, Williams says that she understands the struggles many black women face, because of the discrimination she has personally experienced based on her gender and skin colour.

Serena Williams writes powerful essay calling for equal pay for black women