Today, Nielsen announced that on Oct. 6, they discovered a technical error that impacted national network ratings over the past several months, EW has confirmed.
According to Nielsen’s press release, the technical error came up on March 2, 2014, and went unnoticed until noticing the high viewing levels during fall premiere week. As a result of the error, small viewing segments were miscounted. Cable network and local TV ratings were not affected by the error. The problem was corrected on Oct. 9, and all ratings data from that point forward is correct.
As a result of the error, all released data from Sept. 22 onward will be reprocessed and reissued by Oct. 17, and data going back to Aug. 18, the start of the current fall TV season, will be reprocessed and released by Oct. 31.
The error was due to the AOT with code data (all other tuning with code), which counts for 0.1 percent to 0.25 percent of all viewing minutes nationwide. Usually, the statistical impact of the error is generally small, although the impact is larger in “a handful of cases.”