The comments came in a piece for Porter magazine and were republished by the Guardian. The 22-time Grand Slam champion highlighted the disparity in pay for male and female athletes as a problem: "So when the subject of equal pay comes up, it frustrates me because I know firsthand that I, like you, have done the same work and made the same sacrifices as our male counterparts. I would never want my daughter to be paid less than my son for the same work. Nor would you."
As Ben Rothenberg wrote for the New York Times in April, some of the top tennis tournaments pay men and women the same prize money, but that's not the case across the entire tournament schedule. Below are the top earners to date from the ATP World Tour and WTA:
|Rank||ATP||Prize Money||WTA||Prize Money|
|1||Andy Murray||$13,349,701||Angelique Kerber||$10,136,615|
|2||Novak Djokovic||$12,638,824||Serena Williams||$7,675,030|
|3||Stan Wawrinka||$6,106,954||Simona Halep||$4,333,253|
|4||Milos Raonic||$4,658,492||Agnieszka Radwanska||$4,162,193|
|5||Kei Nishikori||$4,326,748||Karolina Pliskova||$3,976,093|
|6||Marin Cilic||$3,087,205||Dominika Cibulkova||$3,940,433|
|7||Gael Monfils||$2,957,418||Garbine Muguruza||$3,903,388|
|8||Dominic Thiem||$2,880,363||Victoria Azarenka||$2,651,080|
|9||Rafael Nadal||$2,836,500||Petra Kvitova||$2,500,516|
|10||Tomas Berdych||$2,347,055||Svetlana Kuznetsova||$2,396,479|
|Sources: ATP World Tour, WTA|
Williams also argued the perception among the top stars is different between the two genders:
As we know, women have to break down many barriers on the road to success. One of those barriers is the way we are constantly reminded we are not men, as if it is a flaw. People call me one of the "world's greatest female athletes". Do they say LeBron is one of the world's best male athletes? Is Tiger? Federer? Why not? They are certainly not female. We should never let this go unchallenged. We should always be judged by our achievements, not by our gender.
In March, former Indian Wells CEO and tournament director Raymond Moore was criticized after he said WTA stars "ride on the coattails of the men" and should "thank God that Roger Federer and Rafa Nadal were born, because they have carried this sport," per CNN's Ravi Ubha and Matias Grez.
Moore resigned shortly thereafter, but the incident drew further attention to the battle female stars are continuing to wage in order to gain relevancy against their male colleagues.
The gender gap is particularly stark in soccer and basketball.
The United States women's national team earned $2 million total to split for winning the 2015 FIFA Women's World Cup. In comparison, the Germany men's national team took home $35 million after winning the 2014 World Cup. The USWNT has also filed a complaint to the Equal Employment Opportunity Commission against U.S. Soccer over wage discrimination.
In the WNBA, many stars play overseas in the offseason to supplement the income they are receiving in the United States. In August 2015, Vice Sports' David Berri wrote that Dionte Christmas earned $490,180 for playing 198 minutes during the 2013-14 NBA season, while Diana Taurasi made the WNBA's maximum salary of $107,500 for the entire 2014 season.