Nielsen Admits ‘Technical’ Screwup Has Impacted Network TV Ratings Since March

A software fix was deployed on Thursday; all fall data will be reissued

As if TV ratings weren’t complicated enough.

Nielsen has admitted to recently discovering a “technical error” that has impacted national network television ratings over the past several months. It made the find after investigating “recent ratings irregularities,” the company said on Friday.

The error dates back to March 2, 2014, and was “generally imperceptible” before fall premiere week, the TV ratings giant wrote. In the “vast majority” of cases, the impact was minimal, in Nielsen’s words. In some cases, however, it was “more significant.”

Also read: NBC’s Research Prez Reveals New 52-Week Strategy: Original Fall Season Is a ‘Nielsen Artifact’

The mistake does not affect cable and local TV ratings. A Thursday software fix was put in place to correct the glitch going forward.

And fear not, advertisers: all commercial data — including C3 figures — will be correct when it begins coming out this weekend.

To remedy, all fall data — which dates back to Aug. 18 — will be reissued by the end of the month, the company promised. Nielsen is currently running analyses to check if additional weeks should be reprocessed.

Also read: Ratings: ABC’s Shonda Rhimes Lineup Still Strong Against CBS’s ‘Thursday Night Football’

The actual issue stems from “difficult-to-attribute content called ‘all other tuning with code” (AOT with code),'” Nielsen wrote in the mea culpa.

The data represents between 0.1 percent and 0.25 percent of all viewing minutes that it credits nationally.

Also read: Nielsen Touts Mobile Ratings Ready in the Fall, Implementation Ball Is in Clients’ Court

“We are working closely with our clients to manage this situation and will continue to be transparent with the industry and the media about our plans,” the company said. “In addition, we will undertake an exhaustive post-mortem–internally and with our clients–and we are asking Ernst & Young and the MRC to join us in these efforts.”

The release concluded: “Nielsen is committed to upholding the highest standards of television audience measurement and data processing, in order to provide the most effective audience measurement solutions to meet client needs.”