The NFL’s game-day revenues have plummeted in recent years, and this season, the league is facing unprecedented scrutiny over whether it is in fact paying for its games.

A recent study conducted by the sports-book giant Equilar found that in 2015, the NFL’s total revenue was $6.7 billion, down from $8.5 billion the previous year.

Equilar noted that, during the same period, the MLB and NBA had reported $13.9 billion in revenue, while the NHL had $4.3 billion.

Equililar has also looked at the NBA’s revenue over the last five seasons, finding that it lost $2.6 billion in 2015 and $5.1 billion in 2016.

In 2016, the NBA and MLB combined reported $17.2 billion in revenues.

With that in mind, it’s possible that the NFL may have stopped paying its games, which have grown from a $1.9 million average per game in 2014 to $5 billion this season.

The NFL said in a statement to Forbes that the study “appears to be an attempt to draw attention to a number of issues, not an actual analysis.”