In the notice it sent to clients Wednesday, Nielsen said the problem began when it implemented a new method for calculating average audience estimates in its main TV ratings processing system beginning in February, and that it appears to have been delivering "incorrect data for time-shifted data streams" since Jan. 31. Nielsen's so-called C3 ratings, which include time-shifted viewing for three days after a program and its advertising have aired, is the official currency for the national TV advertising marketplace, and the basis for most TV advertising buys and audience guarantees.
Nielsen said it became aware of the problem when clients "inquired about elevated average frequency levels" for the time-shifted viewing data, indicating that the glitch may have over-inflated TV audience estimates.
"This is another embarrassment for Nielsen similar to not picking up the entire URL for their Net Ratings service last year," groused Brad Adgate, the head of research at independent media agency Horizon Media, referring to a major glitch Nielsen disclosed with its online ratings processing in 2010 (Online Media Daily Dec. 2, 2010).
Adgate said the system where the new TV ratings problem occurred, Nielsen's NPower platform, is what most advertisers and agencies use to get their reach and frequency and GRP, or gross rating point, estimates for their advertising buys and guarantees, as well as their "post buy analyses" for evaluating their performance.
Asked if the glitch could lead to makegoods for TV advertising buys, Adgate said, "potentially," but he also noted that the GRP estimates could be processed manually, if necessary.
The timing is unfortunate and ironic, because it comes at a time when Nielsen is making a major push to gain industry confidence - especially among major advertisers and agencies - to make its new Nielsen Online Campaign Ratings (NOCR) the GRP equivalent for online advertising buys (Online Media Daily Sept. 14).
Wayne Friedman and David Goetzl contributed to this story.