What Is Urban? Comparing a Satellite View with the Demographic and Health Surveys

摘要

There is widespread awareness that the world is becoming increasingly urban, both in the share of population living in urban areas and in the geographical extent of those areas. Our understanding of these trends is limited, however, by the lack of both a standard definition of an urban area (UN 2008) and agreed-upon spatial boundaries of urban areas (Balk 2009; Gamba and Herold 2009). This lack of a common framework makes cross-country comparisons and aggregations difficult: researchers may not knowexactly what is captured by a seemingly simple dichotomous urban-rural variable. Illustrating this point, Utzinger and Keiser (2006), in their review of urban definitions used in 228 countries, found definitions constructed using ten distinct sets of criteria. Definitions are most commonly based on population size, economic activity administrative function, or some combination of these. But differences exist even within definitional categories. For instance, although many countries define urban areas on the basis of population size or densities, the thresholds vary.