Population is a gameplay mechanic in Age of Civilizations 2. With higher populations, regular income and amount of recruitable soldiers increase, which is between a tenth and a fifth for a stable province. Populations are identified by countries that can exist in the game by releasing a Vassal or Rebels. For each population in a province, a percentage is defined for which nation that population is a part of. It could say ([80%], Ottoman Empire, [20%], Byzantine empire). Assimilating a province leads to the population being more part of the player's country. Populations can be increased by increasing goods spendings in the Economy Interface, and by disbanding an army group. The disbanding leads to the population increasing by the amount disbanded, and approximately a twentieth are added to the province that it's on directly. Population growth can be increased by building farms, as a part of Buildings. Population can be decreased by recruiting solders, by plundering that province when it is occupied, or not spending enough on goods.
Population can be changed as part of the scenario editor. In an unedited 1440 scenario, Italian countries will have populations in provinces of around 40 thousand, while deserts have as little as hundreds. These can be changed proportionally by a tab. Growth rates for population and economy can also be both increased, and reduced.
When the population reaches the 32-bit integer limit in the positive, it may overflow and become negative. The stability is decreased to 1% when it does this, but the population is made positive the next turn with a positive population growth. If this happens enough time, the proportions of the player country's presence in a population may be reduced, with the size of the population probably returning to tens of millions.