The Causes of Urban Expansion: Global Evidence
Stephen Sheppard[1], Williams College
Shlomo Angel, New York University
Daniel Civco, University of Connecticut
Abstract
In an interesting and comprehensive recent review, Glaeser and Kahn [2004] conclude that urban expansion or sprawl “ultimately has only one root cause: the automobile.” This viewpoint is frequently put forward in both academic writing and the popular press in North America and Europe, and is certainly familiar to urban economists. Nevertheless, we question whether such an absolute conclusion can possibly be correct.
To investigate this issue, we present and analyze a unique (and we believe important) new data set containing measures of urban expansion in 120 cities around the world during the decade of the 1990s. The cities present a sample that is representative of the global population in places with population exceeding 100,000 persons. The measurements of urban land use were based on satellite images analyzed using a technique consistently applied to all images in all locations, thus improving the reliability of measured differences in land use.
After describing the techniques used to measure urban land use, and summarizing the measurements for various regions and types of urban place, we proceed to analyze the data. The first observation is a simple one: urban expansion is a ubiquitous phenomenon, taking place at rates that often dwarf what is seen in U.S. cities even in places where private automobile ownership is relatively rare. More completely, we model urban expansion (both overall and at the urban periphery) as a function of changes in population, incomes, roadways, motor vehicles, linkage to the global economy and function within the local system of cities. We also consider and test whether the process of urban expansion is fundamentally different in different regions of the world or for different levels of economic development.
We find that the phenomenon of urban expansion is more complex than to be attributable solely to one cause.
[1] Department of Economics, Fernald House, Williams College, Williamstown, MA 01267