Definitive proof in the existence of a ‘Taylor Swift effect’ is difficult to pin down, but the NFL Players Association inserted some compelling evidence in its annual filing to the US Department of Labor.

Specifically, the union filing shows a 177-percent increase in group licensing and marketing income for Swift’s boyfriend, Kansas City Chiefs tight end Travis Kelce, who began dating the pop star at the onset of the 2023 NFL season.

In total, the three-time Super Bowl champion earned $2.4 million to rank fourth among NFL players in licensing income, which is generated by everything from video games, trading cards, and replica jerseys.

Kelce’s teammate Patrick Mahomes enjoyed a similar boost in 2023 as his group licensing and marketing income grew 53 percent to a league-high $3.6 million, according to Sportico.

So even though the Chiefs finished the 2022 NFL season with a Super Bowl title, both Kelce and Mahomes saw their royalties skyrocket in 2023 as Swift’s spotlight shined on Kansas City.

Tight end Travis Kelce, left, with quarterback Patrick Mahomes prior to a January playoff game

Taylor Swift and Brittany Mahomes react during a game between the Chargers and Chiefs

There are, of course, other examples supporting the existence of the Swift effect.

For starters, the Chiefs enjoyed a 34-percent increase in online fans this season.

As for the Super Bowl, CBS’ broadcast averaged 123.4million viewers – a record audience for a single network – as Swift watched Kelce win his third Super Bowl in five seasons in Las Vegas. It certainly helped that an estimated five million more women tuned into the game in February than watched the previous Super Bowl.

Former Giants quarterback Eli Manning told Good Morning America in November that the Taylor Swift effect is very much a real thing.

‘I think it makes it fun,’ Manning told GMA’s Robin Roberts. ‘I have three daughters, 12, 10, and 8. When the Chiefs are playing, they are watching that game and looking for Taylor. It makes them enjoy the games and get into it.’

And Manning hasn’t noticed any downside for Kelce, who has been under increased media scrutiny since he began dating Swift.

‘I think he is handling it very well,’ Manning said. ‘You’re dating maybe the most popular person in the world right now, so there’s a lot of questions about it. I think he is handling everything very well. He is staying focused on playing football, doing his job.’

NFLPA spokespeople did not immediately respond to DailyMail.com’s request for the filing.