Some companies (e.g. Amazon) have a policy to fire the lowest performing x percent every year, even if the whole team is good, which makes churn inevitable. It

Some companies (e.g. Amazon) have a policy to fire the lowest performing x percent every year, even if the whole team is good, which makes churn inevitable. It also leads to odd situations like hiring low quality talent just to provide the rotating foundation your real team rests on. And of course constant in-fighting to stay out of the bottom x percent by sabotaging rivals if necessary.