While the general pattern of worker decline and growth is a known part of how the game works, the numbers you provide don’t match up with the known behavior of the game.
That’s not possible unless you have a colony with both surface and orbital population.
A purely surface colony with col cost of zero has only 53.2m workers at 176m pop.
A colony with only orbital pop would have 62m workers at 176m pop.
So 54m workers is only possible with some combination.
If that’s what you have, you should mention it, because mixing surface and orbital pop affects the calculations.
…at 185m is decreases to 50m
Only colonies with col cost over 1.5 will ever see an interval of decreasing workforce with increasing population. But you have far more workers than you would with a col cost over 1.5 (185m pop at cc1.5 gets 40.55m workers).
It is more likely that your colony cost increased over this interval, due to an eccentric orbit.
(The only other explanation is, again, a mix of surface and orbital population. But even with that I don’t think you could cause a drop in worker count just by adding surface pop from 176m to 185m. You’d have to add more surface pop than that, and remove some orbital pop. Maybe. I don’t really want to do the math on this.)
and begins rising again once over 200m…
If col cost is static, any decrease in total workers will not reverse until 240.1m pop (unless col cost 5+, in which case the decrease accelerates with continued pop growth until there are zero workers).
…reaching 54m again at 216m
50m workers at 185m pop implies col cost of ~0.478
54m workers at 216m pop implies a col cost of ~0.365.
So, sounds like an eccentric orbit might be causing most of what you are interpreting as worker losses due to pop gain.
