Shouldn't departments be the appropriate unit of analysis here? Policies after all might differ across units (universities might reward engineering and starve liberal arts, etc.)
With that in mind, I propose the following:
Any department in which there is a consistently high degree of turnover.
My two cents, but that's how one should focus one's search.
A lot of good departments have turnover. If a place has turnover AND no one has gone up for tenure in years because the assistants jump ship, well, maybe you're onto something.
