I have successfully downloaded the GPW global datasets for the years 1990, 1995 and 2000. I would like to know if it is advisable to compare datasets of different years in order to assess changes in population densities and therefore migration patterns, or if there are constraints that hinder such operation.

Many of the population estimates in the GPW data are based on a single census year, while others have had adjustments applied to normalize the data from different census years to a common set of boundaries. This causes problems in inter-annual comparison as many of the changes are artifact from adjustments or reflections of national or regional growth rates rather than net migration or population growth. Because of this, we recommend that you do not use the GPW data for determining migration patterns.

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