Shares of Nielsen Holdings PLC sank 9.8% in active morning trade Thursday, after the New York Post reported that Blackstone Group L.P. had dropped its interest in buying the TV ratings company. Trading volume ballooned to 7.9 million shares, already more than double the full-day average of 3.5 million shares. The selloff put the stock on track for its lowest close since Jan. 3, and the biggest one-day drop since July 2018. The Post said Blackstone's decision comes after months of due diligence.