What Is a City? What Is Urbanization?

In 2008, the United Nations announced that 50 percent of the world’s population now lives in urban areas, a milestone in demographic history.

News reports on the subject frequently rephrased this development slightly to say that half of the global population now lives in “cities” and illustrated articles with photos of Mumbai, Shanghai, or New York. These cities are what the UN terms “mega-cities,” urban areas of 10 million people or more. The distinct impression was created that a majority of people lived in very large cities. However, only about 5 percent of world population lives in the largest cities or, more properly, metropolitan areas. The fact that over half of the world’s population live in places termed urban is a notable development, to be sure. But, at the same time, it is useful and important to know just how the term “urban” is defined.

In most countries, a large part the urban population actually lives in relatively small towns and villages. The urban population may also be thought of more as nonagricultural than urban in the way those in industrialized countries would naturally tend to perceive it. In its most recent urbanization estimates and projections, the UN Population Division recognized that when urbanization is discussed, “the focus is often on large cities, cities whose populations are larger than many countries.” The table below gives examples of how countries themselves define urban. The great variation in the urban definition and the size of places deemed urban is readily apparent (see table).


Selected Urban Definitions With Population Size and Other Criteria

Country Urban Definition
Argentina Populated centers with 2,000 or more
Canada Places of 1,000 or more*
China Cities designated by the State Council and other places with density of 1,500 or more per sq. km.*
India Specified towns with governments and places with 5,000 or more and at least three-fourths of the male labor force not in agriculture*
Japan Cities (shi) with 50,000 or more*
Maldives Male, the capital
Mexico Localities of 2,500 or more
New Zealand Cities, towns, etc. with 1,000 or more
Niger Capital city and department and district capitals
Norway Localities of 200 or more
Peru Populated centers with 100 or more dwellings
Senegal Agglomerations of 10,000 or more
United States Places of 2,500 or more, urbanized areas of 50,000 or more*

* There are some additional requirements regarding population size, population density, and specified urban characteristics.
Source: United Nations Statistics Division, 2007 Demographic Yearbook: table 6.

The UN projects that the world’s urban population will grow by 1.8 percent per year and by 2.3 percent per year in developing countries from 2007 to 2025.1 Both are rather high rates of growth. In fact, by 2020, the world’s rural population will cease growing altogether and begin to decline.

In part, the world’s urban population will continue to grow simply because towns and villages not considered urban today will grow over time. Equally important, migration to urban areas can be expected to increase as economies grow and the likelihood of earning a higher income in cities increases. Much rural-to-urban migration will take place as a result of hardship, as the rural and landless poor make their way to cities and towns in hopes of any employment. One manifestation of such disparate reasons for migration is the Indian mega-city of Mumbai, which contains many of India’s wealthiest celebrities and business leaders and a relatively comfortable middle class alongside the 54 percent of the population living in officially defined slums.

Statistics on the percentage of the world’s population living in urban areas also hide the nature of places deemed urban. For example, “urban” is an entirely different experience in many areas of Africa from what it might be in a developed country. In developing countries, many urban residents live in settlements with little access by road, limited availability of electricity, and little or no access to clean water or basic sanitation. The classification “urban” does not automatically mean that the population has become literate or lost its traditional rural values and social customs. In developed countries, the rural population, on the other hand, often has the same access to amenities and services as urban areas and is almost indistinguishable from the urban other than by location or size of place. Excellent road connections, communications, cable TV and Internet, and access to many of the same services and shopping facilities have rendered the urban-rural difference less relevant in developed countries than it once was.

As with any statistical definition, it is always wise to look “under the hood.” The world is rapidly becoming more urban; the number of mega-cities in the developing world will grow over the next few decades as cities such as Kinshasa, Lagos, and Jakarta are projected to grow to well over 10 million people by 2025. However, “urban” is not a homogenous term and most of the world’s urban population will continue to live in small towns and areas that are a far cry from large cities with skyscrapers and bustling traffic.


  1. United Nations Population Division, World Urbanization Prospects: The 2007 Revision Population Database, accessed online at, on Sept. 28, 2009.