CANNES –  Something dramatic happened to TV viewing about 18 months ago: Aggregate viewing dropped.  This has happened in large part as audiences moved  to video-on-demand and the measurement services which have not been up to the task, says Irwin Gotlieb, chairman of WPP’s GroupM unit.

He says that some 70 percent of the drop in viewership is do to audience “mismeasurement.”

He attributes some of the loss to the growth of IP subscription services notably Netflix.

In this conversation, taped on AT&T Adworks yacht during Cannes Lions, Gotlieb also speaks about the rise of addressable television and new opportunities for advertisers across multiple screens.

He is interviewed by Maria Mandel Dunsche, VP for Marketing at AT&T AdWorks.

Late last year, WPP took a minority stake in TV ratings firm Rentrak.   This year, it took a stake in comScore.

This session about the future of television advertising was presented by AT&T AdWorks in partnership with Beet.TV  Please find additional videos from the session here