Guts of population growth
From Stars!wiki
The pop growth formula has two parts, under 25% and over 25% capacity.
under 25%: popgrowth = population * growthrate * habvalue over 25%: as above, then multiply by crowdingfactor = 16/9 * (1-cap%)^2.
(This formula was posted by Jason Cawley, who credits it to Bill Butler)
