Let's take a look at the 2011-12 season (the fifth overall) of Gossip Girl on the CW.
Rating the Ratings: The CW had one of the most inept seasons in recent memory for a broadcast network, and Gossip Girl was one of its biggest ratings failures. The show's move to the 8:00 hour just didn't go well at all, as it was down huge year-to-year on day one and pretty much stayed that way all season. Gossip Girl was the lowest-rated weeknight drama on the network until The LA Complex came along toward the end of the season, and it couldn't really even lean on great numbers in the young female demos that defined much of its run. In the few W18-34 numbers I saw this season, lead-out Hart of Dixie often did better than Gossip Girl. The positive is that the show did manage to get renewed, as the CW continued its tradition of giving an announced final season to its long-running dramas. Grade: D-.
Here's the now updated War of 18-49 post for Gossip Girl.