Smart people (not necessarily the educated ones) are aware of the strain on finances, time, and energy that children cause. They are more careful, slelctive, and likely to wait until they can devote the time and trouble to raising one or two. Stupid people just like to screw because it feels good. Who drops out more kiddies? Yep, you guessed it.
I have a son, but the "who will take care of you in your old age" arguement holds no water with me. Geriatrics with relatives don't often get visits. Best thing to do is the same thing you do for retirement--plan for it.
I'm sure that this doesn't sit well with most posters on this thread, and I expect that I might hear from some but I really have to go to bed now.