The world's getting too fucking crowded. We need another plague. Or a massive volcanic eruption. Hm, but that's too random. A lot of smart useful people would die. Ooh, maybe... when everyone turns, say, 25, you have to take an IQ test and the bottom third or so are executed. That would force natural selection (force natural? screw oxymorons). Or you could just send them into the military. And no fucking amount of money you have could change it. Ooh, OR, and I've had this idea before, you need an IQ test to reproduce.