Buffalo News has an article on playback devices that are changing viewing habits.
"Naturally, some of the shows with the smallest live audiences have some of the larger percentage gains. For example, the CW’s “90210” had as many viewers watching it later on DVRs as it had watching it live. The total rating was only 1.8.
Two other low-rated CW shows, “Supernatural” and “Smallville,” saw 59 percent and 44 percent gains each but still didn’t hit a 3 rating. But “Gossip Girl” only gained 25 percent here to a 2.0."
Source: Buffalo News.