Abstract:
The Global Rural-Urban Mapping Project, Version 1 (GRUMPv1) consists of estimates of human population for the years 1990, 1995, and 2000 by 30 arc-second (1km) grid cells and associated datasets dated circa 2000. National Identifier Grid is derived from the land area grid to create a raster surface where pixels (cells) that cover the same nation or territory have the same value. Note that the
... countries and territories are not official representations of country boundaries; rather, they represent the area covered by the statistical data as provided. This dataset is produced by the Columbia University Center for International Earth Science Information Network (CIESIN) in collaboration with the International Food Policy Research Institute (IFPRI), The World Bank, and Centro Internacional de Agricultura Tropical (CIAT).
The data in ARC/INFO Binary Grid (GRID), American Standard Code for Information Interchange (ASCII), Band Interleaved by Line (BIL) formats are available from the NASA Socioeconomic Data and Applications Center (SEDAC). 
