The Downsizing of Some American Cities

The Atlantic reports:

Two things happen when a city loses population. The reason for the first is that although a city is often said to be shrinking, its physical area remains the same. The same number of streets must be policed and repaired, sewers and water lines maintained, and transit systems operated. With fewer taxpayers, revenues are lower, often leading to higher taxes per capita, an overall deterioration of services, or both. More people depart, and the downward spiral continues.

The reason for the second is that urban vitality has always depended on an adequate concentration of people. In 1950 the average density in cities like Detroit, Cleveland, and Pittsburgh was more than 12,000 people per square mile; by 1990 it was around 6,000 or 7,000—a dramatic decline. The reality is even worse than it sounds, because the decline was not distributed equally across the city, and certain areas experienced much more dramatic reductions.

Without sufficient concentrations of people, not only is the provision of normal municipal services extremely expensive but urban life itself begins to break down. There are not enough customers to support neighborhood stores and services, or even to provide a sense of community. Empty streets become unsafe, and abandoned buildings become haunts for drug dealers and other criminals. A national study of housing abandonment found that the "tipping point" in a neighborhood occurred when just three to six percent of the structures were abandoned. Vacant lots and empty buildings are more than just symptoms of blight—they are also causes of it.

A big problem for some cities. You'll want to read this article.