Where have millions of US TV viewers disappeared? This fall’s ratings are down 8-10 percemt. “If this is true, it’s a seismic shift. Some of these numbers scare you. And there are billions of dollars in national advertising at stake. When they sell ads, networks pledge that they can deliver a certain number of viewers in certain demographics; if they fail to meet the numbers as tallied by Nielsen, they have to run more ads – ‘make-goods’ – at no cost. If you go back and you look at TV viewing patterns over the past 10 years, it’s very unusual for viewing levels to change more than 2 or 3 percent over time.”