Population growth (the increase of the number of Citizens) is tracked on a per-city basis, and is one of the most fluid elements in the game. It is affected by a number of game systems, but there are three main determining factors: Food, Housing, and Amenities. The Citizen Growth section of the City Details tab shows a comprehensive list of all factors affecting population growth.
- Main article: Food (Civ6)
Availability of Food determines if, and how fast, a city's population can grow. Each Citizen living in a city consumes 2 Food per turn, which forms the city's total Food consumption. This is compared to the city's total Food production per turn, and any excess Food, modified by the various growth factors, is added to the city's current "food basket." This basket measures the progress towards population growth; its size is greater for each successive Citizen after the first. When the food basket is full, the city's population increases by 1. Conversely, the food basket empties each turn that the city does not produce enough Food for all its Citizens, and the city's population decreases by 1 when the basket is empty. If the two factors are balanced, population growth stagnates, neither increasing nor decreasing.
The first section of Citizen Growth shows the current state of all Food modifiers; it also shows the exact amount of Food needed in the current basket for the city to grow. The big bar at the end shows how many turns there are until growth, or loss of a citizen.
There are many ways to increase Food supply in a city, and the more the game progresses, the more ways become available. The game will always keep track of the Food supplies of each city, and issue an immediate alert should you have problems with it.
There is one particular situation in which city growth itself may become the reason for losing a Citizen: if the city's Food surplus is not more than 1 and there are no more tiles to work around the city which provide at least 1 Food, the next Citizen who is born will require an additional 2 Food, thus bringing the Food balance into negative territory. Of course, this situation will be remedied automatically the next turn, when the food basket empties and a Citizen dies of starvation. That is why you should always pay attention to Food alerts appearing among the others.
- Main article: Housing (Civ6)
Housing represents the living space and sanitary conditions available in a city and acts as a soft limit on population growth, as follows:
- If the Housing in a city exceeds its Population by 2 or more, its population growth rate is standard.
- If the Housing in a city exceeds its Population by 1, its population growth rate decreases by 50%.
- If the Population of a city is equal to its Housing or exceeds it by 1–4, its population growth rate decreases by 75%.
- If the Population of a city exceeds its Housing by 5 or more, its population growth stops.
- Main article: Amenities (Civ6)
Amenities represent luxuries and entertainment available in a city and also influence the rate at which its population grows. A city needs no Amenities for its first 2 Citizens; the requirement only appears once the count reaches 3, after which every 2 Citizens beyond that increase the required number of Amenities by one.
- If a city has at least 3 more Amenities than required, its population growth rate increases by 20%.
- If a city has 1-2 Amenities more than required, its population growth rate increases by 10%.
- If a city has the exact number of Amenities required, its population growth rate is standard.
- If a city has 1-2 Amenities less than required, its population growth rate decreases by 15%.
- If a city has 3-4 Amenities less than required, its population growth rate decreases by 30%.
- If a city has at least 5 fewer Amenities than required, its population growth rate decreases by 100% (that is, no growth at all), and you will have much more serious problems in that city as well.
In addition to the factors mentioned above, the Hanging Gardens wonder and the Fertility Rites pantheon directly modify population growth rates (by +15% and +10%, respectively). Also, there are a number of Policies which increase growth indirectly, mainly through boosting the three main growth factors described above.
In Rise and Fall, Magnus' Surplus Logistics title increases population growth by 20% if he is established in a city as its Governor. The Loyalty system also affects population growth, with cities suffering the following growth penalties for low Loyalty:
- -25% if Loyalty is 51–75.
- -75% if Loyalty is 26–50.
- -100% (no growth) if Loyalty is 0-25.
Apart from starvation, there are a few other ways in which a city's population can diminish:
- Conquest. When a city is captured by another civilization, there is inevitably some violence involved, and the city's population diminishes by roughly 25%. It is fully possible for the population of a city which changes hands quickly in the span of several turns to shrink to 1, even if it was large and prosperous before the war.
- Nuclear attack. When an enemy hits a city with a nuclear weapon, some Citizens cannot find their way into bomb shelters, and perish. Thermonuclear Devices usually cause more deaths, since their blast radius is larger.
- Disasters. In Gathering Storm, most disasters cause direct loss of population. Storms can be particularly dangerous, since they persist for three turns and may kill some Citizens each turn; Forest Fires that break out in a heavily wooded area can also kill several Citizens as they spread to nearby tiles.
- Nuclear disasters. Again in Gathering Storm, an incident in a Nuclear Power Plant may cause loss of life (i.e. Citizens) if it is severe enough.
Citizens as workers
Citizens, the products of population growth, are producers as well as consumers. Each Citizen in a city automatically produces 0.5 Science (as of the February 7, 2018 Update) and 0.3 Culture per turn. More importantly, each Citizen can work one tile within the city's borders, adding its yields to the city. Citizens can also work as Specialists, filling slots in buildings in specialty Districts and providing the city with additional Culture, Science, Faith, Gold, and/or Production based on their role. In practice, this means that any given city's productivity mainly depends on the number of its Citizens: the more Citizens, the more land and Specialist slots in the city may be worked, and the more yields added. Note, however, that the special effects of strategic and bonus resources can be enjoyed even without a Citizen working their tile.
There is only one drawback to large cities: they require many more Amenities to remain happy. However, any good governor should be able to easily provide at least the minimum number of Amenities to keep his or her cities normally productive, albeit without bonuses.
As detailed above, the primary factor for population growth is availability of Food. You should always plan ahead and if you intend to settle arid regions (Tundra, Desert), you should attempt to find alternative ways of providing Food. If there is a sea or lake nearby, settle there to use the water for fishing. And if you absolutely have to settle in one of these regions and have no other way to provide a city with Food, separate a Trader or two and establish domestic Trade Routes from the new city.
Even after securing enough Food, there are additional factors to take care of. The best way to keep a city's population growing is to make sure it has enough Housing and Amenities to keep pace with its Food supply. If one wants to create a city with the largest possible population, building Neighborhoods on tiles with high Appeal, placing Entertainment Complexes or Water Parks in surrounding cities so that the central city benefits from their Amenities bonus, and using domestic Trade Routes to provide the city with Food will eventually allow it to grow into a sprawling megalopolis. With the proper layout, it's possible to create a city with a population of well over 100.