I would be willing to bet that advancement to any given level correlates with a certain base level of merit. However, I would also guess that the higher up one goes, the thing that correlates best would be luck. I have no empirical evidence for this other than myself and what I know of people around me, but it definitely rings true to me.

Edit: what a coincidence this is on the front page right now: http://theconversation.com/huge-success-in-business-is-large...