Most widespread faith · 2010
The most widespread religious affiliation by country — a categorical indicator. The coloured category is the terminal denomination in the lead (Catholicism, Orthodoxy, Shia Islam…), never the broad religious family — the distinction that separates, for instance, Orthodox Greece from Catholic Poland, indistinguishable on a map of seven broad families.
World Religion Project (ARDA / Correlates of War), 2010 data point — the only source covering the whole planet on a consistent definition of the terminal denomination. Covers only the 194 sovereign states recognised by Correlates of War at that date; eleven further territories (dependencies, contested entities) were filled in by hand, the rest appears grey "not covered" rather than mixed with a source from another year.
"Most widespread", never "majority": 52 of the 194 covered states have no denomination above 50% (Lebanon 27%, United Kingdom 32%, Germany 31.5%, United States 38%, China 42%). The hover note shows the actual share and explicitly flags pluralities, so the map never lies about more than a quarter of its sample.
Catholicism and Sunni Islam together colour the majority of the world's countries — but the map also reveals globally minor denominations that are locally dominant: Buddhism in Bhutan and Thailand, Hinduism in Nepal, while Sikhism appears nowhere in the lead, since it isn't the top denomination of any sovereign state — the Sikh population is concentrated in an Indian subdivision (Punjab), shown at the sub-national scale.