I have no stats to back this up, but I think there has been a gradual shift in programming over the last few years.
The network channels (ABC, CBS, NBC, FOX) are still the place for comedy, but they are surrendering dramas to the cable channels (FX, TNT, etc.). To make up for this, the networks have shifted to reality programming. Premium channels (HBO, Cinemax, etc.) are the place to watch serial drama such as Dexter, Game of Thrones, Boardwalk Empire, etc.
My viewing habits don't change. I simply go where the quality is.