Olympics ratings fell for the first time since 2000 and advertisers aren't happy

Aside from the Super Bowl, few television stages command as much attention as NBC's broadcast of the Summer Olympics.

It's the sort of broadly appealing, captivating live event that was supposed to remain intact even as traditional television eroded around it, or so popular belief in the advertising industry held.

So it came as a rude surprise when NBC's ratings clocked in much lower than expected last week -- their first dip since the 2000 Games.

"Generally speaking, you're always a little disappointed when it doesn't meet previous expectations," said Adam Schwartz, director of national broadcast and sports media at media-buying agency Horizon.

Worse yet, the missing chunk of TV viewers were more likely to be valuable young people -- millennial viewership declined by a quarter from 2012 -- many of whom migrated to NBC's digital streaming options.

That led to a dramatically bigger-than-expected audience online, where Schwartz said the network charged almost double the per-impression rate of television.

If the trend here was a simple shift from analog to streaming video, it wouldn't be as significant of an adjustment -- NBC could chalk these Olympics up to a lack of foresight and adjust how it sells ads accordingly next time.

But the digital boost isn't enough to fill the hole left in the TV ratings. It's possible that Olympics news and footage circulating on real-time social networks like Snapchat and Twitter and the immediacy of news alerts diluted the appetite for actually watching the games.

"They need new and creative ways to go out and sell it," Schwartz said. "It's a little unfair if you compare it to London, just in the fact that people are consuming television in general so much differently than they did in 2012."

Forrester advertising analyst Samantha Merlivat said brands will need to rethink how they advertise around live events in order to rope together the same sized audience across different platforms.

"It's becoming clear that even live sports audiences are fragmenting across viewing source and devices," Merlivat told Mashable in an email. "For brands this means they need to push TV planning beyond linear to re-aggregate audiences, stitching together audiences across platforms."

Despite the sting felt from the low ratings, Schwartz said NBC did a good job of padding the inventory enough to reimburse advertisers for the losses and most brands didn't take a big financial hit.

Michael Nathanson, an advertising and media analyst at MoffetNathanson, said that concession inventory means NBC may have less to offer in coming months.

He said in a report that the event speaks to television's inability to hold ground against the steady trickle of ad spending from TV to digital.

Still, with so many mitigating factors -- the ill-conceived tape delay, the lack of viewing options for people without cable, problems plaguing the events in Rio -- it's hard to plug the results into one sweeping narrative.

As far as advertisers are concerned, it's still impossible to beat the giant reach of big televised live events.

"People are a bit disappointed, but overall it did deliver some really strong numbers that you don't see anywhere else in the marketplace," says Schwartz.

But the decline does seem to be a clear sign that even television's most important institutions aren't safe as the medium is gradually swallowed by the internet.