NEW YORK — Much of the prime-time audience NBC lost with talk-show host Jay Leno's move has gone not to its rivals but to the digital video recorder.

Rival network executives seemed almost giddy at the possibilities last spring after NBC announced Leno would do a comedy show five nights a week at 10 p.m. There will be more viewers available "for people who put on great dramas," said Leslie Moonves, CBS chief executive, "and that's what we do."

It hasn't quite worked out that way.

NBC's audience at that hour is down sharply, as many predicted. CBS is up six per cent over last season, primarily because it moved the hit series "The Mentalist" into that slot; on three of the five nights, its audience is down. ABC is also down slightly at that hour, and it wasn't exactly overwhelmed with hits last year, either.

With one-third of American TV households now equipped with PVRs like TiVo, the 10 p.m. hour is emerging as a popular time for people to catch up on what they missed earlier in the evening, or earlier in the week.

Here's some math: NBC has lost an average of 1.8 household ratings points at the 10 p.m. hour compared to fall 2008, according to the Nielsen Co. At the same time, PVR usage -- which is also measured by Nielsen -- is up by 1.4 points in that hour.

"The PVR phenomenon is a little bit higher than we thought," said David Poltrack, CBS' chief research executive.

For example, many people watch CBS' "CSI: Crime Scene Investigation" Thursdays at 9, tape ABC's "Grey's Anatomy" at the same time, then watch the medical soap an hour later, he said. They may tape "The Mentalist" (Thursday at 10) for later viewing. One casualty of growing PVR usage is that Friday nights, home of "Medium" and "Ugly Betty," are becoming a TV wasteland because so many people are catching up on programs they missed during the week.

DVR playback is important for programs, yet isn't quite as valuable a commodity for the networks since viewers have the option to fast-forward through commercials.

"You'd rather have a live viewer than a playback viewer," Poltrack said, "but you'd rather have a playback viewer than nothing at all."

NBC will settle for any new viewers it can get for Leno. Here's how rough the neighbourhood is in prime-time: Leno was the universally hailed king of late-night TV this spring and is now a punching bag, with roughly the same number of people watching him. But the standards are higher earlier in the night.

Leno has been deluged with stories judging NBC's grand experiment a failure, and questioning when the network will pull the plug.

Some NBC affiliates are concerned that NBC's 28 per cent drop in viewership at 10 p.m. (through mid-November) is depressing the ratings for the local newscasts that follow Leno on the schedule, and are key to those stations' budgets. Bob Prather, president of Gray Television, which owns 10 NBC stations, said in a call with analysts that the Leno experiment was a failure that NBC isn't ready to admit.

"They gambled," Marc Berman, analyst for Media Week Online, said. "This was the biggest risk I've ever seen a network take in television history. They gambled and they lost."

NBC has said publicly that it needs Leno to achieve a 1.5 audience rating among its target audience of 18-to-49-year-old viewers for the network to make a profit. During Leno's first 40 shows, the ratings dipped below that number 10 times, and equaled it five times.

Leno surprised many people in the industry recently by saying in a Broadcasting&Cable interview that he would have preferred to stay in his late-night "Tonight" show slot, now occupied by Conan O'Brien. He also said he enjoyed being an underdog.

"Emotionally, I can take body shots all day long and that doesn't really bother me," he told the magazine.

And he has defenders. Glenn Abel, a critic for the Web site The Wrap, wrote that he'd seen every one of Leno's shows and it's better than most people think. "Overall, 'The Jay Leno Show' is consistently funnier than 'Saturday Night Live' and is often the most entertaining show in its time slot," Abel wrote.

Over the past week or so, there are indications that Leno may have hit bottom in the ratings and is stabilizing. The show is also gathering some small momentum on Tuesday nights, when a lead-in from "The Biggest Loser" leaves more potential viewers.

NBC has given no indication that it is ready to pull the plug, the way it might for a single night's show. (Network executives weren't made available to The Associated Press to discuss Leno's show.) Downsizing to one or two nights a week would be an admission of failure. There are so many complications: Does NBC pay Leno to go away? Does it pull the rug out from under O'Brien after paying him millions and moving his show to the West Coast?

"I think they have to (ride it out) because I don't think they have a backup plan," said Shari Anne Brill, an analyst for media buyer Carat USA. "What else do they have to go in its place?"