In 2000, the metropolitan areas of the United States collectively housed over 226 million people.
Only 80.8 million of these lived in the "central cities" of their respective metropolitan areas.
The U.S. Bureau of the Census has a spatial unit called the "urbanized area" that is more-or-less solidly built up, and contains suburbs as well as the nation's central cities. The UAs had a population of 200 million in 2000. Thus, the suburbs contained 119 million in 2000, and were far bigger than the central cities that they surrounded.
Beyond the suburbs is an area that is not solidly built up, yet is still considered to be part of the metropolitan area. This area lies in the "shadow" of what looks physically like a city. In U.S. metropolitan areas, the shadow houses another 26 million people.
