GPWv4 ← Knowledge Base How does GPW convert census data into a global grid? 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. I would like to know if it is advisable to compare data sets of different years in order to assess changes in population density over time, or if there are any constraints in using the GPWv4 data 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 grid and the water area grid? When will the grids 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 grids? 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 UN-Adjusted Population Count data sets? Or between the Population Density and the UN-Adjusted Population Density data sets? How should I cite the GPWv4 data? What are the advantages of GPW over other products?