Fox News continues to be near the top in cable television in terms of the number of viewers it attracts, but it is near the top in another category, too: the median age of its audience is among the oldest in television.

For most of the television business — the segment that relies on advertising — that would be serious cause for concern because ad sales are almost always based on a target age of 25 to 54, and Fox News, for the last two years, has had a median age of 65-plus in its ratings both for the full day and for prime time.

But up until now at least, Fox News has been more able than any other television entity to defy the tyranny of the demos, as they are known in the business. And the network, which has upturned traditions and expectations throughout its history, has earned consistently enormous profits, relying on the commitment and loyalty of its audience.

“I don’t think you can fully capture the value Fox News brings by looking at the Nielsen ratings alone,” said Craig Moffett, the longtime financial analyst who specializes in cable. Mr. Moffett, who heads his own firm, said that the key to Fox News’s continued financial strength has been “the level of passion and engagement” it inspires in its viewers.