Oops! Nielsen Appears To Have Generated Incorrect Ratings Data For Most of 2011

By Alex Weprin 

Update: 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.

Original post: The bane of many a TV executive appears to have struck again. According to MediaPost Nielsen appears to have been generating incorrect TV ratings data since February, and only began alerting its clients (read: TV networks and media buyers) this week.

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.

The ratings affected are for “time-shifted data streams,” including C3, which has become the standard currency for TV advertising. C3 measures the number of people that watch a program live, or on DVR within three days of its original airing.

It is unlikely that the screw-up resulted in any major changes to the list of top TV programs, but it could still end up costing networks and advertisers, as Robert Seidman at TVByTheNumbers notes:

I wouldn’t come to the conclusion that the DVR numbers have been vastly overstated (there’s absolutely no chance that’s the case), but the tiniest bit of inflation across all of TV still adds up.

Depending on how many shows were affected and by how much, the result of the glitch could be millions of dollars in “make goods” from TV networks to advertisers.