NCPA - National Center for Policy Analysis


October 16, 2006

High-altitude photos combined with satellite images show that modern American cities are just bigger versions of older American cities, according to a new study.

University of Toronto economist Matthew Turner and his colleagues quantified one component of change in American cities: urban sprawl. They compared satellite images of the entire continental United States in 1976 and 1992, the most recent year complete data were available, and divided the country into 8.7 billion 98-foot squares to examine the question in unprecedented detail.  Their results:

  • Photo evidence revealed that America has grown; nearly 2 percent of the country was paved by 1992 -- a third more than in 1976.
  • However, the percentage of growth that is sprawl is not increasing; although there is more development, on average, that development isn't any more scattered.

Observations of individual cities are also surprising:

  • Miami, for example, is about a third more compact than either New York or San Francisco.
  • Pittsburgh sprawls more than Atlanta or Washington.

Turner attributes about 25 percent of the difference to topographical factors like groundwater accessibility, weather and mountains. The rest is pure human influence: Cities constructed during the automobile era are more scattered, while cities where employment is centralized and taxpayers shoulder more infrastructure costs tend to build on a relatively cheaper and more compact scale.

Source: Anne Casselman, "Is Urban Sprawl an Urban Myth," Discover Magazine, September 2006.


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