The Economist has a fascinating special report about the current and
future state of the TV industry, where they highlight the fact that
most people can't accurately say how they really watch TV, or how much
TV they really watch:
"This helps explain one of the oddest and most consistent findings of television research: people seem unaware of their own behaviour. In surveys they almost always underestimate how much television they watch, and greatly overstate the extent to which they watch video in any other form (see chart 4). In particular, they underestimate their consumption of live television. One of Ms Pearson's subjects, a 27-year-old man, claimed to watch recorded television 90% of the time. In fact he watched live TV 69% of the time."
The whole special report is worth a read.