This analysis has its own flaw. This assumes that their other opportunities are also equal. But tall people may make better apple pickers. And apple picking pays more than egg cracking. If you want 50% tall people, you are going to need to compete directly against the apple picking market as well. You need to account not just for your own selection criteria, but that of everybody else as well. (Not to say this actually explains tech demographics; it's a point about the stats in your example.)