I don't think there are any official statistics about that, you might be better off posting a questionnaire on here and getting people to answer these questions and then finding your own statistics. Yahoo has a pretty wide range of people so you'd get a good number of answers. But from what i know people generally only stay a maximum of a few years and then move on, people outgrown homes quickly. Moving in with a partner, having kids or just genrally moving t want more space as they make more money.
