Urbanization

Urbanization is the process by which an increasing proportion of a country's population lives in towns and city-like settlements. It arises from two sources: migration of people from rural areas to cities, and natural population growth in cities (more births than deaths). Rural settlements can also undergo economic and demographic transformation to become towns without any population movement.

Urbanization is not simply an increase in numbers; it involves changes in lifestyle, work, and land use. Agricultural employment declines while manufacturing, trade, and services expand. Demand increases rapidly for water, electricity, roads, schools, and healthcare.

Measurement

The most common measure is "percentage urban"—the share of population living in places defined as towns. The main difficulty is that the definition of "town" varies by country: some use a population threshold (for example, above a certain number), others base it on administrative boundaries or population density. For this reason, global comparisons require caution. Another measure is "rate of urbanization," the annual percentage growth of that share.

Causes

Scholars commonly distinguish two types of cause: push factors and pull factors. Push factors include land scarcity, drought and climate change, conflict and insecurity, and falling farm incomes. Pull factors include job and business opportunities, healthcare and education services, and family networks already established in cities. Government policy—where factories, ports, and roads are built—also shapes migration patterns.

Effects and management challenges

Cities gain economic benefits from concentration: transport and transaction costs fall, and specialization and innovation increase. On the other hand, when housing and services lag behind population inflow, unplanned settlements, informal land tenure, traffic congestion, air pollution, and water contamination emerge. Fire and disease risk also rise in dense areas.

Global change

Historically, urbanization began gradually with industrialization in Europe and North America in the eighteenth and nineteenth centuries. In the twentieth century and early twenty-first century, the center of growth shifted to Asia and Africa, where many cities now expand rapidly. Very large cities (megacities) with populations in the tens of millions have also appeared.