The stadium was in Vancouver, Canada, but the crowd was chanting “U-S-A! U-S-A!” With a stunning 5-2 score, the U.S. women’s soccer team had just defeated Japan to win the 2015 Women’s World Cup. Midfielder Carli Lloyd and her teammates embraced as confetti rained down on them. Back home, 27 million Americans had tuned in, making it the most-watched soccer match in U.S. history.

For their achievement, Lloyd and her teammates were each paid a bonus of $75,000 by the U.S. Soccer Federation. That may seem like a lot of money. But if the U.S. men’s team had won their World Cup a year earlier, each player would have been paid a bonus of roughly $400,000.

Because of that inequality, Lloyd and four teammates filed a complaint with the federal government last March. It accused U.S. Soccer, which governs the sport in America, of discrimination for paying women less than men—despite equal work and more success. (The women’s team has won three World Cups and four Olympic gold medals; the men’s has won none.)

“When we started to see the men’s contracts and saw the differences in pay, it really opened our eyes,” says Lloyd. 

If the teammates win their case, they could receive hundreds of thousands of dollars in back pay. The impact wouldn’t stop there, says Michael LeRoy, a professor of labor law at the University of Illinois. “The victory would be a landmark that would go far beyond the soccer team” into other sports, he says.

The stadium was in Vancouver, Canada. But the crowd was chanting “U-S-A! U-S-A!” The U.S. women’s soccer team had just defeated Japan. It won the 2015 Women’s World Cup. The score was 5-2. Midfielder Carli Lloyd and her teammates celebrated as confetti rained down on them. Back home, 27 million Americans had tuned in. It was the most-watched soccer match in U.S. history.

For their achievement, Lloyd and her teammates were each paid a bonus of $75,000 by the U.S. Soccer Federation. That may seem like a lot of money. But if the U.S. men’s team had won their World Cup a year earlier, each player would have been paid a bonus of roughly $400,000.

Because of that inequality, Lloyd and four teammates filed a complaint with the federal government last March. U.S. Soccer governs the sport in America. Lloyd and her teammates accused U.S. Soccer of discrimination for paying women less than men. That’s despite the fact that the women are more successful. (The women’s team has won three World Cups and four Olympic gold medals. The men’s team has won none.)

“When we started to see the men’s contracts and saw the differences in pay, it really opened our eyes,” says Lloyd.

If the teammates win their case, they could receive hundreds of thousands of dollars in back pay. The impact wouldn’t stop there, says Michael LeRoy. He is a professor of labor law at the University of Illinois. “The victory would be a landmark that would go far beyond the soccer team” into other sports, he says.

Gender-based wage differences are nothing new in the United States. U.S. Census Bureau statistics show that full-time female workers in general earn about 79 cents for every dollar men make. According to experts, gender pay differences are partly a result of how America’s workforce has evolved over time.

“Historically, we’ve had a male-dominated workforce,” says Angela Lumpkin, professor of sports management at Texas Tech University. “[Men] got there first and established their salaries.”

But pay gaps in sports are especially wide. For example, female soccer players in the U.S. make just 40 percent of what male players make, Lloyd and her teammates say.

By filing their complaint, Lloyd wrote last April in The New York Times, the players were just insisting on “a fundamental American concept: equal pay for equal play. . . . Simply put, we’re sick of being treated like second-class citizens.”

Gender-based wage differences are nothing new in the United States. U.S. Census Bureau statistics show that full-time female workers in general earn about 79 cents for every dollar men make. Experts say gender pay differences are partly a result of how America’s workforce has changed over time.

“Historically, we’ve had a male-dominated workforce,” says Angela Lumpkin. She is a professor of sports management at Texas Tech University. “[Men] got there first and established their salaries.”

But pay gaps in sports are especially wide. For example, female soccer players in the U.S. make just 40 percent of what male players make. That’s according to Lloyd and her teammates.

By filing their complaint, Lloyd wrote last April in The New York Times, the players were just insisting on “a fundamental American concept: equal pay for equal play. . . . Simply put, we’re sick of being treated like second-class citizens.”

Why are gender wage differences so large in sports? Experts say it’s because most men’s sports have more spectators and generate more revenue. (Revenue refers to the total money a sport brings in, from TV rights, corporate sponsorships, ticket sales, and other sources.)

In 2015, for example, the NBA brought in $5.2 billion. According to some estimates, the women’s league, the WNBA, had about $35 million in revenue that same year. Not surprisingly, NBA salaries are much higher.

But conditions are different in soccer. U.S. Soccer projects that 2017 revenue for the women’s team will be about $9 million more than the men’s team. “The facts are out there,” says Lloyd. “We’re generating [more] money.”

Of all sports, men and women are paid most equally in tennis. In its four Grand Slam tournaments, they earn the same prize money.

Yet other tennis tournaments lag behind. For winning the 2015 ­Western & Southern Open in Ohio, Roger Federer earned $731,000. 

Serena Williams, who took the women’s title, received $495,000—68 percent of Federer’s prize.

Williams, one of the world’s most popular athletes, has long insisted on equality. When a tennis official last year suggested that women’s tennis was being “carried” by the men’s star players, she blasted him in the press. The excitement of the women’s competition is pulling in more and more fans, she said, and sometimes outdraws the men’s.

“I would like to see people [in and out of tennis] respect women for . . . what we are and what we do,” Williams said.

Why are gender wage differences so large in sports? Experts say it’s because most men’s sports have more viewers and earn more revenue. (Revenue refers to the total money a sport brings in, from TV rights, corporate sponsorships, ticket sales, and other sources.)

For example, the NBA brought in $5.2 billion in 2015. According to some estimates, the women’s league, the WNBA, had about $35 million in revenue that same year. It’s no surprise that NBA salaries are much higher.

But conditions are different in soccer. U.S. Soccer projects that 2017 revenue for the women’s team will be about $9 million more than the men’s team. “The facts are out there,” says Lloyd. “We’re generating [more] money.”

Of all sports, men and women are paid most equally in tennis. They earn the same prize money in its four Grand Slam tournaments.

Yet other tennis tournaments lag behind. Roger Federer earned $731,000 for winning the 2015 Western & Southern Open in Ohio.

Serena Williams took the women’s title. She received $495,000. That’s about 68 percent of Federer’s prize.

Williams is one of the world’s most popular athletes. She has long insisted on equality. Last year, a tennis official suggested that women’s tennis was being “carried” by the men’s star players. In response, Williams blasted him in the press. The excitement of the women’s competition is pulling in more and more fans, she said.

“I would like to see people [in and out of tennis] respect women for . . . what we are and what we do,” Williams said.

Today, the women of the U.S. soccer team are waiting to see if the government will back them. The case may well end up in federal court.

Labor professor LeRoy says that the women have already accomplished something important. “However this comes out, they have identified a serious problem” in all sports. A victory in court could set a model for other female players to begin fighting their own battles.

According to Lloyd, that is a worthy mission. “We’ve been successful, and we have [influence] now,” she says. “It’s all about helping the next generation of female athletes.”

Today, the women of the U.S. soccer team are waiting to see if the government will back them. The case may end up in federal court.

Labor professor LeRoy says that the women have already accomplished something important. “However this comes out, they have identified a serious problem” in all sports. A victory in court could motivate other female players to begin fighting their own battles.

Lloyd says that is a worthy mission. “We’ve been successful, and we have [influence] now,” she says. “It’s all about helping the next generation of female athletes.”