Nielsen admitted to a software glitch Friday that has impacted its viewing estimates for TV shows this fall, but the problem is not expected to affect ratings focused on the shows' commercials, which have not yet been issued in the new season.
On a press call, Nielsen said a software bug dating back to March has resulted in a small error to its TV ratings. As a result, the software credited viewing to the wrong programs, said Patricia McDonough, senior VP of planning policy and analysis at Nielsen.
But executives described the effect as small, saying 98% to 99% of ratings would be impacted by less than a twentieth of a ratings point, which would be imperceptible in rankings. (A ratings point represents 1% of TV households.) The glitch only affected broadcast ratings, not cable or local stations, the company said.
Nielsen executives declined to say how individual networks may have been impacted by the glitch.
The company will restate ratings from the start of the season on Monday and is discussing with networks whether it needs to reissue ratings further back.
Since "C3" ratings, which describe audiences for programs' ads within three days of their original airing, have not yet been issued for the fall season, the error is not expected to impact evaluation of networks' guarantees to advertisers. The season's first C3 ratings will be released next week.
The admission comes soon after the ad giant WPP Group bought a stake in Nielsen rival Rentrak to sync up Rentrak's TV measurement assets with WPP data and media buying groups Kantar and GroupM. As part of the deal, WPP said it will integrate its consumer data, including Kantar's U.S. digital media and purchase data, with TV information and measurement technology from Rentrak.
Before delving into the software glitch, Steve Hasker, president-global product leadership, Nielsen, took the time to put down Rentrak. Among other claims, Mr. Hasker said Rentrak doesn't have access to as much data as it implies, including demographic data. Rentrak can't provide the same kind of TV currency as Nielsen ratings, he argued.
"They can't do program measurement," Mr. Hasker said. "They can't measure digital or tablet consumption. They can't deliver overnights. And they have no tools to measure out-of-home viewers."
Rentrak measures only about 40% of U.S. households, based on Nielsen's research, Mr. Hasker added. Rentrak isn't currency data and "doesn't act as such," he said, so it only can be used for analytics by WPP or anyone else.
Rentrak CEO Bill Livek said his company, which measures audiences for movies, video on demand and other live and DVR TV, is "merging big data" from such things as auto registrations and third-party data providers Experian and Allance Data Systems to get demographic data it merges with
household TV viewership data.
"The market decides what a currency is," Mr. Livek said. The market wants to have two suppliers competing on ratings just like the credit and securities ratings industries have, he said.
"Hundreds of customers trade on us as the currency in local TV markets, he said, adding that the company also provides "census-based video-on-demand currency."