In the three years after they won the 2015 World Cup, the U.S. women's national team generated more game revenue ($50.8 million) than the U.S. men's national team ($49.9 million), according to audited financial reports acquired by the Wall Street Journal.

Why it matters: The women's team's ability to match, and even exceed, the men's team in game revenue (which is made up of mostly ticket sales) is a key factor in their ongoing gender-discrimination lawsuit against the U.S. Soccer Federation.

Last month, U.S. Soccer responded to the suit by emphasizing that any alleged pay differential is "based on differences in the aggregate revenue generated by the different teams and/or any other factor other than sex."

U.S. Soccer responded to the suit by emphasizing that any alleged pay differential is "based on differences in the aggregate revenue generated by the different teams and/or any other factor other than sex." But the above chart clearly shows that while men's games used to bring in far more money, the women's team has closed the gap in recent years.

Between the lines: Games are, of course, not the only way our national teams generate revenue. There's also sponsorship deals and broadcast rights.

Yes, but: As WSJ points out, "U.S. Soccer sells broadcast rights and sponsorships as a bundle, not separately for each national team. That makes it difficult to parse the value that broadcasters or brands see in the men's team versus the women's team."

The bottom line: Why is this so hard? Give the men and the women the same base salary and then allow them to earn bonuses based on ticket and merchandise sales and anything else that can be tracked.

Go deeper: Meet the U.S. women's national soccer team