Methodologies to Improve Global Population Estimates in Urban and Rural Areas

Deborah Balk, Columbia University
Francesca Pozzi, Columbia University
Gregory Yetman, Columbia University
Andy Nelson, University of Leeds
Uwe Deichmann, World Bank Group

The growth of cities is an intrinsically spatial issue. By 2007, over half of the world's population will reside in urban areas. Despite increasing knowledge about the characteristics of urbanization, little is known about its spatial dimensions, especially at a continental or global scale. This study is the first systematic effort to delineate human population distribution taking into account urban areas and rural human settlements. It employs simple geographic and demographic principles to generate an integrated database (at 1 km resolution) of populated urban extents from census and satellite data for use in studies of urbanization, population, and the environment. This paper describes the data sources and the methodologies used to produce the urban extents and urban-rural population surface. It will also present estimates--including novel spatial ones, such as the proportion of urban dwellers in coastal zones--from the newly created database and compare such estimates to those from the UN.