Population is increased by the number of cities and the number of zones each city has.
|Zone Type||Population Increase|
1,000,000 (for every 1,000,000 sq km)
Because a new city has one of each zone, a new city starts with a population of 19,100.
The max number of zones a cities can have, with a max land area of 5,000,000 sq km provides each city with the opportunity of a maxed population of 195,000,100 people.
Certain events increase your population. This does not increase the number of citizens in your city, but does change your national population.