by Carl Haub, senior demographer, PRB
Few terms in demography can cause more confusion than “urbanization.” News stories reporting projections of world urbanization are nearly always accompanied by photographs of places such as London or Shanghai, and it does seem rather natural to think of urbanization in those terms.
There are really two ways to describe urbanization: urban places and metropolitan areas. Historically, the definition of “urban” has been quite different across countries. In a sense, the urban population was originally more akin to “nonfarm,” although not all people in rural areas worked in farming itself. Considering how the concept of urban-rural began will help in understanding its meaning today.
In the first census of the United States, in 1790, only 5.1 percent of the 3.9 million population was urban and New York was the largest city with 33,000 people. Not until 1920 did the urban proportion pass 50 percent. In 1880, the first figures on the farm population showed that 22 million people lived on farms, 44 percent of the national total and 61 percent of the rural population. The farm population’s peak year was 1910, at 32 million; but today less than 3 million.
Yet, even today, a place of 2,500 or more qualifies as urban. Not exactly Shanghai. But we can see that, as society became more concentrated in expanding metro areas, our way of measuring urbanization underwent changes.
The majority of countries have their own definitions of urban and those definitions vary quite widely. According to the UN Population Division, “It has long been recognized that, given the variety of situations in the countries of the world, it is not possible or desirable to adopt uniform criteria to distinguish urban areas from rural areas.” For example, in Peru, places with 100 or more dwellings are considered urban but, in Japan, the cutoff is 50,000 (the world’s highest cutoff). Those two different definitions place the percent urban in both countries in quite a different light: Japan is 91 percent urban, Peru 75 percent.
The growth of suburban areas adjacent to cities accelerated in the 20th century, leading to the concept of the “metro area.” This definition is most often highlighted in news stories, particularly the UN “mega-cities.” The development of such huge metros as Tokyo and Delhi is a true 20th century phenomenon. But what share of urban population actually lives in such cities?
The table below shows that 9.9 percent of the world’s urban population lived in mega-cities in 2010 (the share is roughly the same for developed and developing countries). But, just over half of the urban population lived in the smallest size category, 500,000 and fewer, and the urban population in the smaller group was more than 5 times larger than in the mega-cities. Globally, only 5 percent of world population (urban plus rural) lived in mega-cities.
World Urban Population by Size of Cities, 2010
|City Population Size 10 Million+
|Number of Cities||23|
|Total Urban Population||352,465,000|
|Percent of Urban Population||9.9|
|Less Than 500,000|
|Total Urban Population||1,826,313,000|
|Percent of Urban Population||51.3|
Source: United Nations Population Division.
Even with the differences, both definitions of urbanization are still useful. While some urban definitions may seem quite small in terms of population size, very often being urban makes a difference: higher levels of education, better paid employment, and smaller family sizes. The metros, or “urban agglomerations,” are often the engines of national economic growth. But clearly we all don’t live in Shanghai!