What Is a City? What Is Urbanization?

by Carl Haub

(October 2009) 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./.../