I play for the first time and killed the entire population in the course of 40 people is added.

Your translation isn't good, but I'll try to respond. Is milord still around? He could maybe help better.

A country with low population will slowly regain population at first, and it will gradually go up. Lowering your tax rate to 0% helps it go up faster. Population growth is based on PCI. Usually takes about 200-250 turns to totally recover, depending on how big you are.

Thank you for the answer.

once you cross 300 population, the number per turn starts increasing from 40.

Once you cross 1350 population(at 0% tax rate), your population starts rising by more than 40 per turn (if you are not bioterrored). If you are at 35% tax rate your max pop growth stays at 40 until somewhere just north of 2050 pop.

Population growth isn't affected by PCI. PCI growth is affected by pop and pop growth in some circumstances and PCI is very marginally affected by population. These effects generally don't matter to the average player.

I was thinking GS/BR hits, returns get higher if you keep pop above 300. thats what happens when you havent played in a couple years.