Transportation, Migration, and Policy as Drivers of Urbanization

Three forces drive urbanization, and they reinforce each other. Transportation matters first: railroads, buses, and roads make it physically possible and affordable for rural people to reach a city and for a city to receive them. Economic opportunity matters second: factories, offices, and informal markets in cities offer wages and work that farming often cannot match, especially once agriculture mechanizes and needs fewer hands. Government policy matters third, and it cuts both ways. Some governments build infrastructure, zone land for industry, or invest in cities directly, pulling people in. Others set land reform, collective farming, or household registration rules that push people out of the countryside or restrict where they can legally settle.

Before 1800, under 10 percent of the world's people lived in cities, because most labor was needed on the land and travel was slow. The Industrial Revolution broke that pattern: steam transport and factory jobs pulled millions into cities across Europe and North America through the 1800s and 1900s. In the twentieth century, the same forces spread to Africa, Asia, and Latin America, and by the early 2000s more than half the world's population lived in urban areas for the first time in history.

That growth is not always matched by jobs. Urban land-use models like the concentric zone, sector, and multiple nuclei models assume cities grow in an orderly way as formal economies expand, but when migration outpaces formal job creation, informal settlements and informal work fill the gap instead.