News Corp.’s Fox network has lost almost 17 percent of its young-adult viewers five weeks into the television season, a drop that threatens to dethrone the ratings leader after six years.

The decline has hit some of Fox’s top shows —”House” is off 34 percent and “The Simpsons” 12 percent — leaving Fox in third place in the 18-to-49-year-old audience that advertisers target, according to Nielsen Co. data supplied by the network.

Fox led at this point last year, as Major League Baseball playoffs and shows like “House” helped build a first-half cushion over CBS. That eased the pressure on “American Idol,” TV’s most-watched program, to carry Fox to victory in the second half. The talent show, which lost 9 percent of its 18-to-49 audience last season, returns in January with new faces and without Simon Cowell — changes that may test viewer loyalty.

“I would imagine that there is a lot of concern over at Fox right now,” said Andrew Donchin, director of national broadcast television for Carat USA, a New York-based advertising company. “I’m sure they’re scrambling to figure out how to fix this.”

 

Viewers sue cable provider

Cablevision, which provides programming in the New York City area, has been sued by three customers seeking damages for the company’s failure to firm up a contract with Fox. Cablevision has been embroiled in a dispute with Fox over fees, and customers face blank screens today for the World Series opener. The dispute is contributing to Fox’s viewer losses.