The venerable TV ratings firm Nielsen Holdings may be going up for sale, with the news that activist investor Elliott Management has taken a large stake in the company in an effort to push Nielsen to put itself up for sale, CNBC reports, citing a report by The Wall Street Journal.

“Elliott has accumulated an 8 percent stake, which could be worth at least $640 million, in Nielsen, sources told the Journal,” CNBC reports. “Multiple private-equity firms have shown interest in Nielsen, the Journal said, citing the sources.”

CNBC adds: “Elliott believes that Nielsen’s ‘buy’ segment, which measures retail and consumer behavior, has failed to keep up with competitors like market research company IRI, the Journal reported.”

The report also notes: “A spokeswoman from Nielsen told the Journal that the board welcomes the views of its owners, including Elliott, as it continues to evaluate how to best position the business.”