The broadcast TV business has had a rough run this season and next season isn't looking much better. Starting from last fall when their new shows debuted, all four major US networks saw a drop in viewers in the age 18-to-49 demographic, the group most prized by advertisers, The Wall Street Journal reports today. Fox saw ratings for this group decline 23 percent through March, ABC's ratings declined eight percent, NBC's by seven percent, and CBS's by three percent. As audiences tune out of broadcast, analysts fully expect that advertisers will follow them.

Ad sales for cable TV eclipsed broadcast in 2011 and the gap has only widened since then

We'll know more after broadcast and cable TV companies present their new shows to advertisers in May for pre-sale time, but the trend is clear: ad sales for cable TV eclipsed broadcast in 2011 and the gap has only widened since then. Of course, it's not just cable that broadcast has to worry about. Analysts told the Journal that advertisers will likely move some of their buys from broadcast and cable to web video outlets.

For an even younger demographic, web video seems to be the clear first choice. Last year, in Netflix-subscribing households with children, audiences were larger for Nickelodeon content on Netflix than on Nickelodeon's own cable channels, according to figures cited by AllThingsD today. That move goes against the assertions of Netflix and Nickelodeon's parent company Viacom, both of which have argued that streaming re-run content helps convert Netflix viewers into cable TV viewers. The latest numbers certainly don't help that argument, but until TV companies come up with a viable Netflix alternative, they may have to just sit back and continue to watch their audiences and advertisers move online.