Nielsen finds errors in TV ratings

Nielsen NV, the television research firm being challenged by Rentrak Corp., said it discovered errors in national network ratings and will reissue results for the new TV season.

An internal investigation found problems with data going back to March 2, Nielsen said today in a statement. The company will revise results going back to Aug. 18, and has asked Ernst & Young LLP and the industry-backed Media Rating Council to join the probe. Cable and local TV ratings weren't affected.

While the errors were small, they threaten to dent Nielsen's standing with networks as the gold standard used to set prices for almost $70 billion in annual TV advertising. Rentrak is making acquisitions in audience measurement and signing clients like CBS Corp. as it steps up competition.

"They are small numbers, but have significant effects," David Poltrack, CBS's head of research, said of the Nielsen mistakes. "It's certainly not trivial."

Poltrack said he suspected the numbers were inaccurate when ratings came in for the season premiere of "Dancing with the Stars." He called Nielsen, which uncovered a software glitch.

Previous discrepancies weren't large enough to reveal the error, which executives of New York-based Nielsen said on a call were minuscule for the vast majority of shows.

"What we saw as we went into fall season with new lineup is a difference between affiliate ratings and network ratings we could not explain," Pat McDonough, Nielsen's senior vice president of planning policy and analysis, said.

CBS criticizes

Poltrack criticized Nielsen for minimizing the mistake.

"It's a blatant attempt to hide the impact," he said.

Nielsen officials said they held the call to be open about the error, while declining to answer questions about reports that ABC benefited from the ratings snafu. Revised ratings will be issued Oct. 13.

"Our entire industry relies upon Nielsen for accuracy and veracity, and we hope that they can quickly resolve this issue," ABC, the broadcaster owned by Walt Disney Co., said in a statement.

Nielsen also criticized Rentrak, which agreed Thursday to buy the domestic business of measurement firm Kantar Media from WPP Plc and has been making inroads in TV ratings. That deal boosted Rentrak stock 12 percent while Nielsen fell 4 percent.

"Our friends at Rentrak never let facts get in the way of a good press release," said Steve Hasker, Nielsen's global president.

Nielsen rose 1 percent to $41.70 at the close in New York. The stock has lost 9 percent this year. Rentrak fell 0.3 percent to $71.84 and is ahead 90 percent year-to-date.