Bottom-up gridded population estimates for Nigeria, version 2.1

This README file provides information about the data included in the data release, how it was produced, source data that were used, and known assumptions and limitations of the results.

This zip file contains 40 geotiff rasters at a spatial resolution of 3 arc-seconds (approximately 100 m). Each raster provides gridded population estimates for an age-sex group per grid cell across Nigeria. We provide 36 rasters for the commonly reported age-sex groupings of sequential age classes for males and females separately. These are labelled with either an “m” (male) or an “f” (female) followed by the number of the first year of the age class represented by the data. “f0” and “m0” are population counts of under 1-year olds for females and males, respectively. “f1” and “m1” are population counts of 1 to 4 year olds for females and males, respectively. Over 4 years old, the age groups are in five year bins labelled with a “5”, “10”, etc. Eighty year olds and over are represented by the groups “f80” and “m80”. We provide four additional rasters that represent demographic groups often targeted by programmes and interventions. These are “under1” (all females and males under the age of 1), “under5” (all females and males under the age of 5), “under15” (all females and males under the age of 15) and “f15_49” (all females between the ages of 15 and 49, inclusive). These data were produced using age-sex proportions from the WorldPop project (WorldPop et al., 2018). The age-sex proportions were applied to the gridded population estimates 3(NGA_population_v2_1_gridded.tif) to allocate the population to the different age-sex classes. While this data represents population counts, values contain decimals, i.e. fractions of people. This is because both the input population data and age-sex proportions contain decimals. For this reason, it is advised to aggregate the rasters at a coarser scale. For example, if four grid cells next to each other have values of 0.25 this indicates that there is 1 person of that age group somewhere in those four grid cells.

This geotiff raster, at a spatial resolution of 3 arc-seconds (approximately 100m at the equator), contains estimates of total population size per grid cell across Nigeria. NA values represent areas that were mapped as unsettled based on a gridded settlement layer derived from building footprints (Maxar Technologies, Inc. and Ecopia Tech Corporation, 2021). These data are stored as floating point numbers rather than integers to avoid rounding errors in aggregated population totals for larger areas.