This study examined the dynamics of global urban expansion by defining a new universe of 3,943 cities with population in excess of 100,000 and drawing a stratified global sample of 120 cities from this universe. Population data and satellite images for two time periods - a decade apart - were obtained and analyzed, and several measures of urban extent and expansion - among them the built-up area of cities and the average density of the built-up area - were calculated. Data for 90 cities out of the global sample of 120 is presented and analyzed in this report. Weighted averages of the built-up area and the average density, as well as compactness and contiguity measures - and their change over time - are presented for nine regions, four income groups and four city size groups covering the entire globe. Densities in developing-country cities were found to be some three times higher than densities in cities in industrialized countries, and densities in all regions were found to be decreasing over time. If average densities continue to decline at the annual rate of 1.7% - as they have during the past decade - the built-up area of developing-country cities will increase from 200,000 km2 in 2000 to more than 600,000 km2 by 2030, while their population doubles. Ten econometric models that sought to explain the variation in urban extent and expansion in the universe of cities were constructed, and several hypotheses postulated by neoclassical theories of urban spatial structure were tested. All tests yielded R2 values in excess of 0.80. The policy implications of the analysis are presented and discussed. The Central message of this study is quite clear: Developing country cities should be making realistic - yet minimal - plans for urban expansion, designating adequate areas for accommodating the projected expansion, investing wisely in basic trunk infrastructure to serve this expansion, and protecting sensitive land from incursion by new urban development.
This research was supported by the World Bank’s Urban Development Division under the project The Urban Growth Management Initiative: Confronting the Expected Doubling of the Size of Cities in the Developing Countries in the Next Thirty Years, and by the National Science Foundation under the project The Causes and Consequences of Urban Expansion.
Dr. Shlomo Angel, PI
Adjunct Professor of Urban Planning, Robert F. Wagner School of Public Service at New York University, New York, NY and Woodrow Wilson School of Public and International Affairs, Princeton University, NJ
Dr. Stephen Sheppard, PI
Professor of Economics at Williams College, Williamson, MA, focusing primarily on markets for land and location, location choice by firms and households (including migration), and how these are affected by environmental factors and the public sector.
Dr. Daniel L. Civco, PI
Professor of Geomatics at the Department of Natural Resources Management and Engineering, University of Connecticut, Storrs, CT. Dr. Civco is an earth resources scientist with considerable experience in remote sensing and GIS applications. Dr. Civco is Director of the Center for Land use Education And Research (CLEAR) at the University of Connecticut, and is the founder of its Laboratory for Earth Resources Information Systems (LERIS).
Research Assistant at the Department of Natural Resources Management and Engineering, University of Connecticut, Storrs, CT.
Research Associate at the Department of Natural Resources Management and Engineering, University of Connecticut, Storrs, CT, and Director of the Laboratory for Earth Resources Information Systems (LERIS).
Academic Assistant at the Department of Natural Resources Management and Engineering, University of Connecticut, Storrs, CT.