Through work I had the privilege of being around lots of people who were smarter than me, but if somebody asked me to rank them from "somewhat smarter" to "much smarter", I would have had a hard time.
Just an anecdote! I don't have any hard evidence.
I also wondered for many years why most of them didn't quit their jobs when on paper they would have been able to do so, but work is not a great place to ask those sorts of questions.