Instant population growth of 20% of your max pop if you are under 50% of your max pop
What if this calculated on the next tick after WD, as opposed to immediately upon WD? People would have a chance to build in a lot of cases and take advantage of this mechanic.

Alternatively what if the boost were prorated; anyone <=50% gets the full 20% boost, but someone at 75% gets a 10% boost, someone at 87.5% would get 5%, etc...