Stating the obvious
I thought this was an obvious point. But maybe it is not: A tenure rate of less than 50% is not attractive.
Suppose you are 30-something years old, and have moved all over the country and/or world for your career already, having done undergrad, masters, PhD, and postdoc in different locations. Would you rather go to a university where your colleagues expect you to get tenure and will support you in getting there, and the assumption is that unless something goes pretty wrong, you’ll be able to stick around after the first 5-6 years? Where you could maybe buy a house and expect to keep it for a while? Or would you rather go to a university where on average, only 50% of professors get tenure? That’s a one in two chance of getting kicked out.
Some people will always go for the more prestigious university, even if the tenure rate is low. Those universities can offer concrete (if potentially temporary) advantages. But I think that many (in particular, women and two-career couples) who would rather not be subjected to yet another high-stakes "testing" process at this stage of their lives, with the possible downside being another job search, period of uncertainty, and possible cross-country move five years later.
