Change of population density

The map is based on the Gridded Population of the World, Version 3 (GPWv3), consisting of estimates of human population for the years 1990 and 2010 by 2.5 arc-minute grid cells. A proportional allocation gridding algorithm, utilizing more than 300 000 national and sub-national administrative units, is used to assign population values to grid cells. The population density grids are derived by dividing the population count grids by the land area grid and represent persons per square kilometer Source: CIESIN & CIAT