Every 1K infra up to 5K (and I think it starts back up at 8K) the cost/upkeep jumps a fair bit (usually 10%). For the first jump I'd say about 4-5 mil would be plenty.
Only gained like 1K people. Just jumped the 4K Barrier, bagging about 300 infra, and bought some 150+ miles of land to boot, but my population ONLY went up about 1K people.
Isn't that a bit low?
Anyway, for some unknown reason, I just lost 5K people I didn't loose any trades, or tear down any improvements, or change my government. I didn't even buy/sell infrastructure.
Proof:
My nation
Any ideas?
A comment on Chruches/Intel Agencies. Intel Agencies are better as they are a bit cheaper and give you +100 spies. Churches are only better IF you have your taxes below 23% for some reason.
How does land size play into population anyway?
Also, I remember at one time with a small amount of modifiers (like cattle) 1 infra=10 people. I guess that was changed