Nielsen Nielsen

Nielsen has admitted that, after some "ratings irregularities," the company has uncovered a technical error that has impacted network ratings for months.

"The technical error was introduced on March 2, 2014, and was generally imperceptible until we saw high viewing levels associated with fall season premiere week," Nielsen said in a statement. "As a result, small amounts of viewing for some national broadcast networks and syndicators were misattributed. Cable networks and local TV ratings were not affected by this error."

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On Thursday morning, a software fix was employed to correct the error. All previously released data since Sept. 22 will be reprocessed and reissued by Oct. 17 and all data going back to Aug. 18 will be reprocessed and reissued by Oct. 31.

The company added that in most cases the impact was minor.

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