I'm not sure if that exact statistic is listed in his recent book, but a very similar one is... IQ by occupation by race. Charles Murray's "Facing Reality". I

I'm not sure if that exact statistic is listed in his recent book, but a very similar one is... IQ by occupation by race. Charles Murray's "Facing Reality". It includes many tables of statistics that may interest you. Note that despite a lot of anger toward him, I've read several of his books, and he goes to great lengths to state that he doesn't believe we should discriminate against people based on their race. I highly recommend reading his books rather than listening to commentary about them.