Urbanization

Urbanization describes how much of a province lives in towns and cities rather than on the land. In the demographic model it is the single most powerful influence on population growth: as a society moves into dense industrial centres, housing costs and the shift away from farm labour bring family sizes down.

How urbanization is determined

Urbanization is not a slider or a building. It follows each province's GDP per capita on a logarithmic curve:

• At $600 per person or less, a province is fully rural (0%).
• At $20,000 per person or more, it is fully urban (100%).
• In between, each doubling of income moves it the same distance along the scale. A province reaches 50% at roughly $3,500 per person.

Because of the logarithmic shape, the first steps out of poverty urbanize a province quickly, while wealthy provinces creep toward the ceiling. Anything that grows a province's Economic Output – industry, Infrastructure, modern equipment, good government – also, in time, urbanizes it. Anything that wrecks its economy, such as Devastation or Occupation, does the reverse while it lasts.

Effect on growth

A fully urban province grows about 1.8 percentage points a year more slowly than an otherwise identical rural one. Against a baseline of 2.2% a year, that is most of the difference between a fast-growing agrarian society and a slow-growing industrial one. The 1946 settings were fitted to real postwar growth, and urbanization turned out to carry most of the difference between countries.

The province view's Population Growth tooltip shows the province's current urbanization among the inputs of its growth rate.

In practice

• Rich countries grow slowly. The industrial democracies start the campaign largely urban, so their natural growth is low regardless of policy. The Postwar Baby Boom modifier is what lifts the United States, Canada, Australia and New Zealand above that until 1964.
• Developing countries face a moving target. Industrialization raises output and tax revenue, but it steadily lowers the birth rate, and with it the long-run growth of the workforce and of Manpower.
• Cities and politics. Urban, wealthy provinces vote differently from the countryside, since party affinities follow GDP per capita and population size. See Factions.

Related systems

The planned Migration system would let people move toward richer provinces, which would concentrate population in the most urban parts of a country. It is not yet built.