Fox News's ratings among 25- to 54-year-olds is the lowest it's been in 12 years, even as the cable channel remains the highest-watched of all its competitors.

In May, Fox News attracted an average of 264,000 primetime viewers in that key demographic. The last time their 25-54 ratings were so low for a single month was August of 2001, or just before the September 11th attacks. Although Fox News's individual shows continue to win out over their competitors, May produced decade-low numbers for their primetime and morning hosts, particularly in the 25-54 demographic used by advertisers. And that's why those figures matter so much: Fox News's audience is still relatively huge, but it's taking in smaller numbers of the only viewers ad buyers pay attention to. 

The New York Times took a look at the results for Bill O'Reilly's show, which remains popular with overall audience of 2.1 million viewers. But in the key demographic, he averaged just 313,000 viewers, a small percentage of his overall pull. His show's median viewer age is now 72.1, which is a high. That's part of a trend. Fox News's viewership is aging out of that key demographic, even as the overall median age of cable news viewers remains high: the median ages for the three cable networks in May were 62.5 (MSNBC), 62.8 (CNN), and 68.8 (Fox News). 

But at least Fox News can say it's remaining steady as the most-watched cable news network, even with its shrinking and aging audience. Now that CNN has exhausted every possible angle into the missing plane story, the network's ratings — which were, as usual, well below Fox News's — plunged from a pretty good April. MSNBC beat CNN's numbers overall and in the 25-54 demographic. As the Times notes, both networks experienced some notable lows in May: CNN's had the worst-rated 9 p.m. primetime slot in its history, and MSNBC's primetime numbers were its worst since 2006.