Nielsen Acknowledges Ratings Measurement Problem…

MediaPost’s Joe Mandese writes about a new problem at Nielsen…

A week after unveiling an aggressive plan to convince the ad industry to use its new Facebook panel as the “GRP” for online advertising and media buys, Nielsen Wednesday began informing clients about a major snafu with the one that generates GRPs for the multibillion television advertising marketplace. Nielsen said the glitch has been generating incorrect data for most of this year for GRPs and the reach and frequency estimates used as the basis for most TV advertising plans. Nielsen said the problem is under investigation, but some agency executives already believe it could lead to big problems with their TV audience guarantees that could result in millions of dollars in “makegoods” from television networks.

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.

Update: TVNewser’s Alex Weprin reports that the problem isn’t as pervasive as first reported…

Good news! It appears that the actual error is far less of a problem than MediaPost reported. It does not affect C3, and is limited to a system that is not typically used for advertising purposes. In other words, it likely won’t cost TV networks any money.