I think this a good topic, I've seen it debated before. I think a more logical way of controlling population than just abortion would be to choose several times in a person's life (ex: 1yr, 5yrs, 10yrs, 25, 50) and weed out the mentally or physically troubled and unproductive individuals. It might also be beneficial to have a cut off of around 75 to 80 as the maximum age for a person. Of course, the more undesirables we could eliminate at earlier stages, the more expedient it would be.
It all sounds awfully science fiction. Then again, it did happen in Nazi Germany to a somewhat lesser extent... the intellectual center of the world at the time.