The The Gridded Population of the World, Version 4 (GPWv4): Population Count consists of estimates of human population, consistent with national censuses and population registers, for the years 2000, 2005, 2010, 2015, and 2020. A proportional allocation gridding algorithm, utilizing approximately 12.5 million national and sub-national administrative units, is used to assign population values to 30 arc-second (~1 km) grid cells. The population count grids contain estimates of the number of persons per grid cell.