EPAR Technical Report #388
Thu, 05/30/2019
Ayala Wineman
Didier Alia
C. Leigh Anderson

Designing effective policies for economic development and sustainable rural transformation, and monitoring progress toward the associated policy goals, often entails categorizing populations by their rural or urban status. Yet there exists no universal definition of what constitutes an "urban" area; countries alternately apply criteria related to settlement size, population density, or economic advancement. In this study, we explore the implications of applying different urban definitions in Tanzania and Nigeria, drawing from a wide set of data sources (administrative, remotely-sensed, and survey-based) to understand how urban categorizations align across data types and based on different criteria. To understand how an analysis of rural change is affected by the urban/rural definition applied, we begin with the nationally representative Living Standards Measurement Study - Integrated Surveys on Agriculture (LSMS-ISA), collected in Tanzania (2008-2014) and Nigeria (2010-2015). This data set contains rich information on household demographics and income-generating activities, and crucially contains household geo-coordinates. Nine urban definitions are assessed, based on local administrative designations used by the National Bureaus of Statistics in Tanzania and Nigeria; settlement size (drawing from the Africapolis geospatial database of cities in Africa); population density (drawing from WorldPop); night lights intensity (drawing from the NOAA Nighttime Lights of the World dataset); impervious surface cover (drawing from the NASA Global Man-made Impervious Surface dataset from Landsat); local economic orientation (drawing from the LSMS-ISA); and our subjective assessment of daytime satellite imagery available via Google Earth.

Preliminary results indicate that the urban population share can vary considerably across different definitions, ranging from 11-35% in Tanzania and 20-60% in Nigeria. Nigeria is often found to be more urbanized than Tanzania, although this ordering is reversed for two definitions. In Tanzania, most urban definitions applied are relatively conservative, as compared with the administrative categorization. Thus, it is rare to see segments of the population re-categorized from rural to urban when using another definition, though some officially urban households are recategorized as rural. In Tanzania, these definitions sometimes lead to different conclusions regarding the concentration of poverty in rural versus urban areas, alternately indicating that poverty is increasingly a rural or urban problem. They also produce somewhat diverging stories regarding trends in welfare and farm income shares in the rural population. For example, while most definitions suggest that a growing share of rural homes now access electricity, this time trend disappears when using an economy-focused definition. The pace at which rural households have been shifting away from agriculture (a key component of structural transformation) is estimated to be twice as fast when relying on a night lights urban definition, as compared to the local administrative definition. At the same time, these different definitions paint a consistent picture of the rural farming population in terms of levels of engagement with input and output markets. This reflects the manner in which definitional decisions especially affect the categorization of non-farming (though possibly rural) households.

Type of Research: 
Data Analysis

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