Sweeps

30th Anniversary this fall. They brought in the ratings and cheesecake back then!

3-4 times a year it's Sweeps when the Nielsen Ratings are on the scene especially during Watershed (Prime Time).  Scripted shows, reality shows and the news alike will all seem to have an "If it bleeds it leads" mentality geared towards sensationalism hoping to lure more viewers in. February has the Super Bowl, awards shows, mid-season and more while in May it's Season Finales (on terrestrial anyway).  July is quieter as it's summer and not everyone wants to be home so much yet cable has their new seasons.  November is getting closer to the festive period and the new season has everyone settled in.  If you ask me every month now seems like Sweeps and 25% of the year Double Sweeps.
Some may argue that the meter and print survey method of gathering Nielsens is getting dated.  PBS can seem exempt from ratings even though Downton Abbey (from commercial ITV in the UK) will bring them in anyway.  There must be technology now that can tell if people are tuning in even with their DVRs or devices.  Some shows are fish in a barrel while others they're not biting and lead to the axe.  If almost no one's watching anymore then it's better to cut their losses though some people will always complain.  Otherwise, if it pays, it stays.