There are a few top level names that come to mind who were professionals that contributed to other fields, but I think if you looked at all GMs and averaged it out, it wouldn't be common.
Take the top 10 players today for example, what do they do besides chess?
I read an article saying that Bobby Fischer was an "idiot chess savant". From what I understand, it means that Chess Grandmasters excel in other fields other than chess ,whereas Bobby Fischer, because of his mediocre education, excelled in nothing else but chess and outside of chess did not really contribute much to any other field. Your thoughts and comments would be very interesting.