IQ was mentioned a couple times in the film, and the main character was shown studying very hard to keep up with his job. The fact that it wasn't the sole focus of the selection program was a consequence of the whole society wanting to do it. It wasn't a bunch of super-nerds doing something weird, the idea was that every part of our society's conception of achievement and "human quality" had been folded in to the nightmare, which made it inescapable.