National level population is one of the few topics for which both historical and projection data are easily found online. Both sets of data are often found on the same site. Data can include total population, crude birth and death data, age and sex structure of populations, infant and under-5 mortality rates, etc. Some of the historical data goes back to 1950 while projections are often made to 2050 or 2100. The World Bank, the United Nations and the US Census Bureau are the main providers of free national population data. Recently, sub-national data, including GIS shapefiles, have become increasingly available. These new sources are being added to this page.
World Bank The World Bank has a number of databases containing population data. Many of the databases can be accessed in more than one way, either through the common search facility or as Excel or CSV files which have been made up of selected indicators (Note that the preselected downloads often do not include all of the indicators in the database.) A main data page which gives access to the databases as well as a host of other information from the Bank is at https://datacatalog.worldbank.org However some users may find this page confusing. There are two main approaches to getting data, searching and downloading from the database or downloading the already prepared selection of data. The following databases which contain population data have a common interface for searching-- World Development Indicators (WDI) and Global Development Finance (GDF) (which have been combined for searching); Gender Statistics; Health and Population Statistics; African Development Indicators; and Millennium Development Goals. The search engine can be accessed directly at http://databank.worldbank.org/data/databases.aspx .
World Bank data on sub-national populations (at the state/province level) is available at http://databank.worldbank.org/data/reports.aspx?source=subnational-population.United Nations (Urban/Rural) -- Data on the urban/rural indicators related to the Millennium Development Goals is available at http://unstats.un.org/unsd/mi/mi_goals.asp . While other urban/rural population data including long-term projections is available from the Population Division data bases at http://www.un.org/popin/data.html
US Census Bureau --The US Census Bureau provides a wide range of materials including a downloadable database of demographic data including projections to 2050. The main page giving access to the various sources of data is http://www.census.gov/population/international/data// .
Gapminder -- Gapminder is an innovative data presentation web site which provides dynamic views of data changes over time using bubble graphs. Graphs are available for economic, population, health (including HIV/AIDS), environmental, agricultural and information technology data. Raw data can be downloaded from the site and a desktop version of the software is available free. Users can customize graphs using existing data, but cannot add new data. Much of the data used is from the World Bank and UN organizations. Gapminder is at http://www.gapminder.org .
UNFPA-- The United Nations Population Fund, publishes an annual report on the State of World Population. This report is available as a pdf file on their website at http://www.unfpa.org/swp/ . Previous reports starting with 1996 are available at from a link on the same page.UNFPA also present a dashboard of populationited options for downloading data at https://www.unfpa.org/data .
City Population-- This is a private site which provides data on
city populations as well as populations at different administrative
levels. It also provides area data which permits the calculation of
population densities. The data is not presented in a directly
downloadable form but can usually be saved to a spreadsheet through a
select/copy/paste operation. Finding the data you want may take a bit of
searching on this site which is available at https://citypopulation.de/
Nordpil-- Provides population data and projections to 2050 for for the world's major cities--the data is available as a spreadsheet or shapefile. Click https://nordpil.com/resources/world-database-of-large-cities/.
DHS-- Demographic and Health Surveys provides a wealth of demographic and health information at the sub-national level both as spreadsheet data and shapefiles. The data available and dates depends on the type of survey carried out. The data is available at http://spatialdata.dhsprogram.com/data/#/
National Statistical Offices --A list of links prepared by the United Nations to the websites of National Statistical Offices and other providers of statistics at the individual country level is available at http://unstats.un.org/unsd/methods/inter-natlinks/sd_natstat.asp and WTO also provides a list at http://www.wto.org/english/res_e/statis_e/natl_e.pdf. These offices often have subnational population data.
International Institute for Applied Systems Analysis -- The IIASA provides population projections in the context of the Sustainable Development Goals at http://www.iiasa.ac.at/web/home/research/researchPrograms/WorldPopulation/SDG_Scenarios_2016.html.
International Conflict Research--This organization provides a collection of "253 near-continuous maps of local ethno-linguistic, religious, and ethno-religious settlement patterns in 47 low- and middle-income countries" at https://icr.ethz.ch/data/side/.Data and raster format maps are available for downloading. A knowledge of "R" would be useful to use this site.
Harvard University -- Harvard provides shapefiles on religions at https://worldmap.harvard.edu/data/geonode:wrd_province_religion_qg0.
University of Toronto-- Shapefile maps on religion can be downloaded from http://maps.library.utoronto.ca/cgi-bin/files.pl?idnum=423&title=World+Language+Mapping+System+Version.