I would assume that it's due to a limited number of companies having useful IP to steal. I have had similar experience with several companies, and hear similar

I would assume that it's due to a limited number of companies having useful IP to steal. I have had similar experience with several companies, and hear similar stats from those who work with other companies, but that is anecdotal. I would also hazard a guess that many companies don't want to admit it, even if it does happen.