This is an older article, but I just came across it. Think you're above average? That doesn't bode well!
http://www.damninteresting.com/?p=406
Note: all this reminded me of the Peter Principle. One of the posters makes reference to it, but it resulted from the studies of a UBC professor who realized that if you do good at your job, you will be rewarded with a promotion. If you do well at that job, another promotion. This continues until you reach a position you're
not good at and there you stay. We are, Dr Peter said, promoted to our levels of incompetence.
For the record, he was studying education systems.