There's a very simple reason why women participating in the recent World Cup don't earn as much money as their male counterparts — because there's less interest in watching women's sport.

But that hasn't stopped the Left from complaining about the pay disparity. In a fundraising email sent Friday, the Democratic Congressional Campaign Committee demanded that "Congress close the pay gap and give women equal pay for equal work."

The thing is, women's soccer generates far less interest — and therefore less revenue — than men's soccer. The Left likes to point out that the World Cup between the U.S. and Japan brought in 25 million viewers, but the Federalist's D.C. McAllister points out that the viewership probably has more to do with the U.S. being in the championship than with any general interest in women's soccer.

"So a U.S. team in a World Cup final had more viewers in the United States than a World Cup final in which no Americans played. Does this surprise anyone?" McAllister wrote. "Can we really compare a World Cup final that includes an American team with a match that doesn't? Apples and oranges, folks."

Beyond the viewership argument, women's soccer brings in far less revenue than men's. Fox Sports pulled in $17 million in ad sponsorship, compared to $529 million that ESPN brought in for the men's final last year. The men's World Cup also brings in $4.5 billion in direct revenue to FIFA.

A suggested solution has been to have FIFA promote women's soccer more. It'd be difficult to find many people who are unaware of women's soccer. FIFA would first have to spend money to generate interest, but since that interest doesn't currently exist, why spend the money?

McAllister noted that viewership for the Olympics is high every four years, but that doesn't mean people are going to start attending swimming competitions or track meets.

A championship every four years may give bored activists a reason to complain about inequality, but it is ultimately close to meaningless in determining interest in the sport and whether female athletes should be paid disproportionately to the revenue they earn for their organizations.