Cable and ratings

Is there two-way communication between one’s cable box and the cable company? That is, can the cable company tell what channel you’re watching? If so, is the information used for ratings purposes? If that is so, what about people like me, who leave the box on all the time so as to record things? Wouldn’t that skew results?

This is just guesswork but I assume ratings go the other way. Nielsen does cable ratings, so I assume cable companies get their ratings from them (or similar surveys) and pass them to the viewer. It would be easier and cheaper, plus a lot of cable companies are local or regional, so ratings derived from their viewers would probably disagree with national ratings from time to time if they gathered ratings on their own.

I would also assume the cable company does use that info internally in some manner. I can’t imagine a company passing up the chance to use data like that for something.