I don't get TV ratings! I mean, they don't mean anything to me. I don't watch a show because it is advertised as the highest rating TV show ever.. WHATEVER!
BuddyTV has a good article about the rating of Supernatural. It basically talks about how DVR ratings are saving my favorite shows like Supernatural and Smallville.
"The traditional Nielsen ratings might say that shows like NCIS and Grey's Anatomy are on top, but when it comes to younger audiences and non-traditional ways of watching TV, the CW is way out in front..." Full article at BuddyTV.
So only older people still watch TV when it's on, younger audience will DRV or iTune it whenever they want.