Glitch in Nielsen systems ‘overestimates TV viewing figures’

Mediapost reports that the firm sent a note yesterday explaining that the problem began in February when a new method for calculating average audience measurements in the main TV ratings processing system was introduced.

As a result, incorrect data for Gross Rating Points (GRPs) and the reach and frequency estimates used for TV advertising plans has been produced, the firm reportedly told customers.

Nielsen said that since then it has been delivering “incorrect data for time-shifted data streams” – which could include the C3 rating that is the official currency in the TV marketplace.

The company did not return calls seeking comment.

• Editor’s note: Nielsen issued a statement after this story was published saying: “There is no impact to C3 commercial data, ratings and projections, electronic data files used by other processors, or to reach or any other NPower-reported data.” NPower is the data processing system affected by the glitch.