It would be nice to know the exact formula, but atm I am grabbing at any bit of info on the relation between colony cost->population->manufacturing->economy and everything in between.
I understand the basics, colony cost determine your max population, which determine your manufacturing capabilities and wealth production through trade. But all the intricacies allude me ![Embarrassed :-[](http://aurora2.pentarch.org/Smileys/classic/embarrassed.gif)
Your workforce is divided into Agriculture/Environmental + Service Sector + Manufacturing = 100%. Manufacturing are the people you get to use for stuff like factories or research labs or mines.
As mentioned, Agriculture/Environmental scales with Colony Cost - it bottoms out at 5%, and goes up by 2.5% or something per 1 Colony Cost.
Service sector percentage scales with population. I think it's at about 400-500 million where it caps out at 75% of your population. I'm not sure the exact formula is known, since the last posts were a long time ago and it may have changed.
It's because of the way that service sector scaling works that moving people off of Earth is so useful - if you have 1 million spare workers on Earth, you can pick up 4 million people and drop them on colony and have 3 million available workers. It's worth it to move people off of Earth to a developing colony on an Ideal Habitable World until you hit 250M people or so. At that point you're not gaining much in terms of lower service sector needs.
EDIT: For Trade, supply and demand scale with population. Each world produces surpluses in different things. There are breakpoints at which colonies begin to demand specific goods, and I think it's 10M and 25M. A colony of size 1M only wants a fraction of the trade goods, a colony of size 11 million has demand for most of the trade goods, and a colony of size 26 million wants some of every type of trade good. So for ideal trade, you want multiple 25M+ worlds that specialize in different things so they can trade between them.