US ad-supported broadcast and pay TV networks saw more ratings declines in the third quarter of the 2017, according to analysis from MoffettNathanson and Nielsen. 2017 is the third year in a row for linear TV networks to suffer significant live TV rating falls, and we’re beginning to see the effects of those declines in content production. TV network advertising in Q3 is down 10%, and Nielsen’s C3 ratings for primetime viewership among viewers aged 18-49 is down 14%. Cable networks have fared much better, according to MoffettNathanson’s analysis. Cable networks saw only a 4% dip in primetime viewing. Broadcast networks are down 18.5% over Q3 2016, which Michael Nathanson has dubbed “the greatest decline over the past six years.”…