• by David Goetzl  @dgoetzl, April 5, 2006

Top network shows lose a considerable portion of their audiences during commercial breaks, according to Nielsen data obtained by MediaDailyNews.

The data, an analysis of Nielsen's so-called minute-by-minute ratings, shows the audience for CBS hit "CSI" dropping 15 percent during commercial breaks in February.

Among adults ages 25 to 54, "CSI" averaged a 9.5 Nielsen rating for the month during programming, but only an 8.1 rating during commercial breaks.

"CSI" is the No. 1 show on CBS. The top shows on the other major networks also lost viewers during commercials, though at a lesser rate than "CSI."

Fox's "American Idol" Tuesday edition--the number-one show on television--saw 25-to-54 ratings fall 8 percent for the month, dropping from a 13.2 to a 12.1.

On ABC, "Desperate Housewives" fell 6 percent from a 10.9 in the programming to a 10.2 during commercials, while "ER" on NBC also dropped 6 percent, going from a 7.1 to a 6.7.

Advertisers in general prefer the adult 18-to-49 demo, but 25-to-54 is an important target for many marketers. Ratings could fall even further in the 18-to-49 demo during commercials since younger viewers may be more rabid ad skippers.

Ratings guarantees are based on program averages, so the lower commercial measures could provide fodder for advertisers increasingly looking to prove that people are viewing their ads. On the network side, a revenue slide corresponding to the ratings drops could mean a loss of millions of dollars.

Advertisers are expected to press networks in the coming upfront to base some guarantees on the so-called "commercial ratings," while networks are likely to resist.

Minute-by-minute ratings are not new, but have been available since last fall in a more user-friendly fashion. So far, however, The Weather Channel is the only network known to have purchased the new offerings, while on the buying side, only Starcom MediaVest and ZenithOptimedia groups have acknowledged receiving them.

Minute-by-minute data was a hot topic at the recent American Association of Advertising Agencies' Media Conference.

Jean Pool, executive vice president-COO at Universal McCann and chair of the AAAA's Media Policy Committee, told networks to make the ratings available or risk appearing as if they are "trying to hide some dirty little secret. In the end, we want commercial ratings, not program averages," she said.

But while speaking to reporters at the conference, Mike Shaw, ABC's president of sales and marketing, said the issue is "a two-way street," and if advertisers want to employ minute-by-minute ratings, they must bear the burden of creating more compelling ads--including in HD--to prevent viewer exodus during breaks. "They better start coming up with some better creative," he said.

The issue has not only divided buyers and sellers, but sparked some rift among sellers. The Weather Channel, for example, is making the argument that it has strong viewer retention during commercials in its upfront pitch. Liz Janneman, TWC senior vice president, has even suggested the network would be willing to base guarantees on the minute-by-minute data if an industry standard for attaching values emerges. "The more we can provide accountability to our clients, the sounder they'll feel their investment will be with us," she said.