Those are good points Gods_dice, and Chuck’s response is very valid as well. I’ll add two other points that may argue against improvement in the early years:
1. Today’s anti-selectors may not have better results than in earlier years because the best of them will no longer need to anti-select due to more effective treatments for their impairments.
2. There may be more people needing to anti-select than before because they’re still alive; their illnesses would have already killed them in earlier years.