Diane Haithman interviewed Community creator and show runner Dan Harmon for Deadline's Emmy series. It is an interesting read, but his comments on Nielsen Ratings are just more gasoline on the fire of incorrect perceptions about ratings measurement (as well as more squares for Fan Excuse Bingo!).
DEADLINE: Did it [episodes like 'Chicken Fingers' and 'Paintball'] help in terms of ratings for the second season?
HARMON: It did not work in terms of ratings at all. Nothing we really do works in terms of ratings. As far as critical respect goes, you can see a meteoric upward curve happening in the second season. If I only looked at our Nielsens, I wouldn’t even know that our show was on the air, much less if it was doing better or worse, because our audience is that small. The Nielsens were invented when television was splitting 200 million people three ways. Now, if somebody’s cat happens to turn on the TV, my numbers can double. It’s almost unrelated to what’s really happening.
While the premise that Nielsen was created at a time when fewer people were split among only a few channels is true, cats are incredibly discerning in that worldview! They vastly preferred Idol, NCIS, The Big Bang Theory, Jersey Shore and The Office to Community, Chuck, Detroit 1-8-7, V and The Event.
While it's reasonable to say Nielsen doesn't do a great job of measuring overall popularity of a show (when including viewing outside of TV), Nielsen isn't around to measure popularity to satisfy fans and show runners, it's around to broker advertising sales. It has room for improvement on that score too, but as often as not networks and advertisers aren't willing to pay for things that would improve measurement (e.g. so far very few networks have signed up for Nielsen's new service that combines online and TV viewing within three days of telecast provided that the same national ads ran online as on TV).
It's the notion that Nielsen isn't effective at measuring what happens in terms of TV viewing that is "unrelated to what's really happening."
The good news for Community fans is that ratings probably won't play a huge factor in whether it gets a fourth season, at least if it winds up with a full 22 episodes for its third season. Shows that are a full season (or less) away from syndication at the end of three seasons are almost always renewed for a fourth season to get them to the 88 episodes that are considered the minimum for Monday-Friday "stripping" in syndication.