In my experience this happens very rarely. In most places that I'm aware of, there is a very strong aversion to hiring local candidates for tenured (or tenure t

In my experience this happens very rarely. In most places that I'm aware of, there is a very strong aversion to hiring local candidates for tenured (or tenure track) positions. For example, in Germany it is extremely rare to become a professor at the. University where you did your phd/postdoc. It's almost always seen a something not quite right. Now there is still lots of politics involved in the hiring process. Tenured positions are rare and often the other academics on the committee want to candidates which strengthen their own research area (although interestingly if there is a colleague down the corridor or someone at a university half way around the world who can do some technique you require, collaboration is much more likely to happen with the external person)