GPWv4 ← Knowledge Base How is a global raster created from tabular census data and boundaries? How does GPWv4 compare to previous versions of GPW? What source data is used in GPWv4? Are there any published papers about GPWv4? What are the restrictions on use and redissemination of data? GPWv4 releases data for five years: 2000, 2005, 2010, 2015, 2020. Is it advisable to compare data sets of different years in order to assess changes in population density over time? Are there constraints in using the GPWv4 target year data sets as a time series? What is the projection used for the GPWv4 data? What does a zero in the population density grid mean? What does No Data mean? How was the Data Context layer created? What is the difference between the Water Mask layer and the Water Area layer? When will the rasters of census variables (sex, age, and urban/rural designation) be released? Why does Egypt look different than the rest of northern Africa in the population count and density rasters? Can I use GPW to study how population in Syria and the surrounding countries is being affected by conflict? What is the difference between the Population Count and the UNWPP-Adjusted Population Count data sets? And between the Population Density and the UNWPP-Adjusted Population Density data sets? How should I cite the GPWv4 data? What are the advantages of GPW over other products?