1 Urbanization: Concepts and Global Patterns

What urbanization means

Urbanization is the process by which an increasing share of a population lives in urban settlements. It is about the distribution of people: a city’s population may increase without a country becoming more urban if rural populations grow just as quickly. Conversely, the urban share can rise when people move into towns or when settlements are reclassified as urban.

Urbanization is related to, but distinct from, urban growth and urban expansion. Urban growth is an increase in the number of people living in urban areas; urban expansion is the outward spread of built-up land. These processes often occur together, but neither is identical to a rising urban share.

How urban places are classified

The meaning of “urban” varies across countries. National statistical agencies use different criteria, including population size, density, administrative status, and economic activity. As a result, urbanization percentages calculated using different national definitions should be compared with care.

For more consistent comparisons, the UN’s 2025 World Urbanization Prospects also uses the Degree of Urbanization method. It classifies settlements using population grids, density, and contiguity. In this system, cities have at least $50{,}000$ people and a density of at least $1{,}500$ people per square kilometre; towns and semi-dense areas have lower thresholds, while rural areas are less densely populated or lie outside these settlements.

Historical shifts in urbanization

Cities have existed for millennia, but for most of human history the great majority of people lived in rural communities. Large-scale urbanization accelerated with industrialization. From the late eighteenth and nineteenth centuries, factory production, expanding trade, transport networks, and administrative growth concentrated work and services in cities.

Rural-to-urban migration and growing urban populations first transformed settlement patterns in Europe and North America; urbanization accelerated later in other regions. During the twentieth century, urban populations grew rapidly in Latin America and parts of Asia. Many countries in Africa and Asia entered especially rapid urban transitions later.

In some countries, cities grew faster than industrial employment or infrastructure. Rapid urbanization therefore did not automatically bring broad-based prosperity or adequate housing and services.

Processes that drive urbanization

Several processes can contribute to urbanization at the same time:

• Rural-to-urban migration: People move to cities and towns for employment, education, healthcare, safety, and other opportunities. Rural poverty, environmental pressures, conflict, and displacement can also drive migration.

• Natural increase: Births exceeding deaths add residents to cities, including people whose families already live there.

• In-situ change: A settlement can gain population density, infrastructure, and non-agricultural jobs while residents remain in place. It may then function as, or be classified as, urban.

• Reclassification and boundary change: Governments may designate a settlement as urban or extend a city’s administrative boundary. This can increase measured urban population without people moving.

• Economic and transport change: Industrialization, expanding services, trade, transport links, and public investment can concentrate jobs and connect surrounding settlements to urban centres.

For example, a fast-growing town may attract migrants, experience natural population increase, expand outward, and eventually meet a statistical threshold for classification as a city.

Global population patterns

The UN’s harmonized estimates show a long-term shift among cities, towns, and rural areas. In $1950$, about $20\%$ of the world’s population lived in cities, $40\%$ in towns, and $40\%$ in rural areas. By $2025$, the shares were about $45\%$, $36\%$, and $19\%$, respectively. These figures use Degree of Urbanization categories and are not directly interchangeable with urban shares calculated under each country’s national definition.

The UN estimates the world population at $8.2$ billion in $2025$. Under the Degree of Urbanization classification, $45\%$ lived in cities, $36\%$ in towns, and $19\%$ in rural areas. The city category alone is not the same as the total share living in urban settlements: cities and towns together account for most of the population in this framework.

Where urban growth is occurring

Urban growth is geographically uneven. Many of the world’s most rapidly growing cities are in Africa and Asia, and growth is not confined to megacities. The UN counts $33$ megacities—urban areas with $10$ million or more people—in $2025$, more than half of them in Asia.

Small and medium-sized cities greatly outnumber megacities. Among roughly $12{,}000$ cities analyzed, $96\%$ have fewer than one million residents. The number of cities worldwide more than doubled between $1975$ and $2025$. The UN projects that it could exceed $15{,}000$ by $2050$.

Projections and urban needs

The UN projects that about two-thirds of global population growth from $2025$ to $2050$ will occur in cities, with most of the remainder in towns. The global rural population is expected to peak in the $2040$s and then decline. These are projections, not guaranteed outcomes.

Growing urban populations increase demand for housing, water, transport, energy, schools, healthcare, and employment. Outcomes depend on how growth is managed. Investment and inclusive planning can expand access to jobs and services, while inadequate planning can intensify congestion, insecure housing, and unequal access to urban opportunities.

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