For years television networks and advertisers worried that viewers weren’t watching commercials nearly as often as programs. Those worries were largely put to rest by recent ratings that showed the falloff in viewing from network primetime programs to commercials was actually about 7 percent.

Now it looks as though any celebrating on the part of media sellers and advertisers was premature.

Ratings just released by TiVo, the DVR-maker, suggest the falloff in ratings from program to commercial is much steeper. TiVo viewers are not only fast-forwarding through recorded commercials. They're also simply turning off commercials when watching shows live in their original broadcast.

These dismaying findings come from TiVo's StopWatch service, which tracks second-by-second viewing on 20,000 of its DVRs.

These new findings would seem to contradict data from Nielsen Media Research of average ratings for commercials airing within programs showing only modest viewership falloff from programs to commercials, that 7 percent figure.

Certainly part of the difference stems from the greater propensity of TiVo owners to zap ads. A good share of the general TV-watching population lacks the ability to zap ads even if they wanted to.

But it also suggests that Nielsen's data may be showing higher ad viewing levels than actually occur.

While TiVo is only releasing top-line data from its findings, they're revealing in what they show.

For example, the May 3 episode of ABC’s "Grey’s Anatomy" pulled a 24.9 rating in TiVo homes, but the highest-rated commercial in the show, Carefree Hair Remover & Moisturizer, generated only an 18.9 rating, a decline of 24 percent, according to StopWatch.

In another example, a Burger King spot on the April 18 episode of Fox’s “American Idol” pulled a 15.3 rating, compared to a 20.8 rating for the program, a 26 percent difference. And that was the highest-rated commercial in the entire month of April.

This new TiVo data is sure to revive arguments about the value of Nielsen's commercial ratings, which are based on the average rating for all commercials airing in a program and can include parts of shows as well for ads on either end of the commercial pod.

“Commercial ratings, the way Nielsen is doing it, as an average, is a transition rating,” says Tracey Scheppach, senior vice president and director of video innovations at Starcom USA. “[The industry] has to move to actual commercial ratings, as opposed to average commercial ratings.”

But there are exceptions to the commercial falloff as tracked by TiVo's Stopwatch. Odd as it may seem, some ads do better than the shows in which they air.

A Ford truck commercial on the May 23 episode of “Idol” generated a 27.9 household rating, compared to a 23.1 rating for the program. On March 27, a commercial for the DreamWorks movie “Disturbia” pulled a 21.1 rating on “House” while the program itself had a 20.2 rating.

As one might expect, StopWatch found that the falloff for commercial ratings was more pronounced when TiVo viewers watched recorded programs.

“Something like 50 percent to 70 percent of commercials are generally fast-forwarded among viewers who are watching on a time-shifted basis,” says Todd Juenger, vice president and general manager of TiVo Audience Research and Measurement.

The May 3 airing of “Grey’s,” for example, generated a 17.3 time-shifted rating, but the Carefree Hair Remover commercial in that episode only pulled a 10.1 rating, a decline of 42 percent.

“There are a couple of rules of thumb,” says Juenger. “The higher the rating is for a show, in general, the more time-shifting it has, although there are exceptions. And the broadcast networks, as opposed to cable networks, generally have more time shifting and of the time-shifted programs, more fast-forwarding of commercials.”

The StopWatch ratings underscore the need, as Starcom's Scheppach argues, for even better means for tracking viewing of commercials, with Nielsen's commercial ratings but a step in that direction.

The just-concluded upfront ad market was largely negotiated with Nielsen’s new average-commercial-minute ratings and ratings generated from the original airing of a program plus three days of DVR-recorded viewing, which have become known as C3 ratings, instead of program ratings.

TiVo's Stopwatch won't replace that system because it's limited to viewers of its DVRs, not the wider, representative audience advertisers need in a ratings system. But it will serve media buyers well in their efforts to pressure Nielsen into improving its system.