Let's take a look at the 2011-12 season (the eleventh overall) of Family Guy on Fox.
Rating the Ratings: Though Family Guy remained the biggest piece of Animation Domination for another year, its 15% year-to-year drop was one of the worst in recent years. In label terms, it went from "easily a hit" to "barely a hit." Though the show had never gone below a 3.0 demo from its revival in 2005 up through the sixth episode of this season, it never even broke a 3.0 once in the final ten episodes of this season, and its penultimate episode of the season scored just a 2.4. Last year, I said the drops didn't mean much but were something to keep an eye on. Ditto for 2011-12. Grade: C.
Here's the now updated War of 18-49 post for Family Guy.