World Religions Map – 1900 to 2050

1900: the world bar – from the World Christian Encyclopedia. There are no country figures for 1900, so the map shows only an estimate of the largest religion in each country, based on its earliest data and known corrections (for example: most people in sub-Saharan Africa then followed traditional religions, and in communist countries almost everyone then belonged to a religion). Countries without a good basis for an estimate are grey.

1950–1990: the Correlates of War World Religion Project (Maoz & Henderson). A country not yet independent takes its earliest year, and a year the source rates "low reliability" gives way to a nearby, better-rated year – the country details say which year the data are from. Russia before 1991 is the whole USSR. This source and Pew define "unaffiliated" differently: in China, Japan and Vietnam Pew counts as unaffiliated also people who keep folk or Buddhist practices without belonging, so a jump between 1990 and 2010 there comes from the definition, not from real change.

2010 and 2020: Pew Research Center estimates (2025), based on more than 2,700 censuses and surveys. 2030–2050: projection. Pew's 2015 and 2025 reports use different methods (for example, far more people in China are now counted as unaffiliated), so for each country we took the updated 2020 figure and added the change Pew projected from 2020 to that year. Projections assume that today's trends – fertility, age, migration and switching between religions – continue; unforeseen events can change them.