Changes and trends in urban sprawl in the United States 1970 - 2010

The past decade has highlighted potential associations between urban sprawl and human health as well as environmental impacts associated with the built environment. Sprawl has been implicated in obesity, physical inactivity, transportation mode choice, global climate change and other outcomes. This study examines changes in urban sprawl in United States metropolitan areas from 1970 to 2010 using a sprawl measure based on the differences in population between high density and low density tracts. Overall, levels of sprawl have increased over this period, but the rate of increase has dramatically decelerated since the 1970s, declining from an almost 23% increase in the 1970s to only a 2% increase in the 2000s. Considering individual metropolitan areas, there are several different sprawl trajectories. Some metros continue to have high rates of sprawl increases, others (the majority) have settled into steady state or have modestly changing levels of sprawl, and a small number of metropolitan areas have become denser since 1970. Regression analysis shows that 1970 sprawl levels, western location, median household income, and center city population change had an association with 2010 sprawl. African American and Hispanic population percentages, southern location, and percent of the workforce employed in manufacturing were not associated with 2010 sprawl levels. These divergent histories suggest sprawl may be neither inevitable nor irreversible. They may mean that metropolitan specific conditions or policies might impact sprawl and that modifying these might result in improvements to sprawl related health and environmental issues.