Nielsen, the company that the television industry and advertisers rely on for ratings, said Friday that months of ratings for national broadcast networks could be wrong.
"In response to recent ratings irregularities, Nielsen conducted an extensive internal investigation of our systems and processes," a press release said. "On Oct. 6, 2014, we uncovered a technical error that impacts national network television ratings over several months." The company said this error did not affect cable networks or local television stations. Nielsen said it will reprocess all of the impacted data going back to Aug. 18.