How the mighty have fallen. Fox, which usually wins the top 18-49 rating for the entire TV season, has been forced to give up its thrown to CBS, which won bragging rights today. With just a few days left in May sweeps, CBS has already claimed victory.

CBS said that for the first time since 1991 - 21 years ago - the network earned the top average rating for a season in the key 18-49 demographic. It averaged a 2.9 rating over the course of the season. It also averaged 11.85 million viewers, giving the network another season to call itself ‘America’s Most Watched Network.’ The network has had that title for 10 of the past 11 years.

While CBS did get the Super Bowl this season, the network has had amazing success with its scripted programming. NCIS is still the most-watched drama on network TV, while tHe Big Bang Theory frequently beat Fox’s American Idol on Thursdays.

Speaking of Fox, the network averaged a 2.5 18-49 rating, dropping 22 percent. Not only was Idol a flop, but in the fall, The X Factor failed to draw viewers, notes The Hollywood Reporter.

ABC and NBC also saw drops, reports EW. NBC was naturally going to see its numbers drop despite The Voice, since it had the Super Bowl during the previous season. ABC could blame Dancing with the Stars, which it wil lbe cutting to just one night next season.

Here’s the full chart:

18-49 demo
CBS - 2.9 rating (3 percent drop)
Fox - 2.5 (22 percent drop)
NBC - 2.4 (4 percent drop)
ABC - 2.2 (8 percent drop)

Total Viewers (in millions)
CBS - 11.849 (up 1 percent)
ABC - 7.848 (6 percent drop)
Fox - 7.059 (20 percent drop)
NBC - 6.964 (6 percent drop)

image: CBS