Let's take a look at the 2011-12 season (the sixth overall) of Rules of Engagement on CBS.
Rating the Ratings: We live in a world where the Live+SD average for entertainment programming drops at least 7% every season, so it's pretty rare to see an individual show in the green that has to sweat out a renewal like Rules of Engagement did. The renewal didn't come till well after the upfronts, and it's for yet another short season in yet another unspecified midseason timeslot. Then again, it's not like this was a totally shocking piece of year-to-year growth since the show's The Big Bang Theory lead-in was up by more than 20%. Rules was most impressive late in the fall when it came on in relief of bomb How to Be a Gentleman, posting a mid-3's level for much of that run that was its highest consistent level in three years. The show likely struggled to the renewal because it was so much less noteworthy in the spring, typically hitting around a 2.7 when it had a mid-4's BBT lead-in. Still, it'll remain the only of the Thursday BBT lead-outs to ever eke out a renewal, and it's now done it twice. Grade: B-.
Here's the now updated War of 18-49 post for Rules of Engagement.