A new analysis of 201 countries and territories reveals shifting patterns of religious diversity worldwide, with the United States ranking as one of the most diverse nations, according to a report released Friday by the Pew Research Center. The study, which builds on data from a 2025 report detailing changes in the global religious landscape between 2010 and 2020, introduces a Religious Diversity Index (RDI) to quantify the distribution of major religious groups within each country.
The RDI, a modified version of the Herfindahl-Hirschman Index, assigns a score from 0 to 10, with higher scores indicating greater religious diversity. The index focuses on seven categories: Christians, Muslims, Hindus, Buddhists, Jews, adherents of “other religions,” and the religiously unaffiliated. Pew Research Center researchers limited the analysis to these seven groups to facilitate comparisons across nations, acknowledging that a more granular breakdown – accounting for denominations within Christianity or branches within Islam – would yield different results. For instance, the report notes, the U.S. Score would be higher if various Protestant denominations were counted as separate groups rather than aggregated under “Christians.”
The methodology involves a three-step calculation. First, the proportion of each religious group is squared and summed, representing religious concentration. A country with a single dominant religion would score 1 at this stage, even as an evenly distributed population across all seven categories would score 0.14. This score is then subtracted from 1 to reflect diversity and finally, inflated by a factor of 11.6 to produce the final RDI score on a 0-10 scale. The Pew Research Center’s methodology is detailed further in a supplementary document outlining the calculations here.
The RDI score is determined by both the dominance of a single religious group and the evenness of distribution among others. A country with 70% belonging to one faith will have a lower score if the remaining 30% are concentrated in a single category, but a higher score if spread across five or six others. The resulting scores are categorized as “remarkably high,” “high,” “moderate,” “low,” or “very low” diversity. Countries in the “very high” category have no single religious group exceeding 57% of the population, while those in the “very low” category are dominated by a single faith representing 96% or more of the population.
Alongside the RDI, the Pew Research Center also calculated a “religious divide” score using the Reynal-Querol index. This index measures the extent to which a country is evenly split between two religious categories, ranging from 0 (virtually everyone belonging to one religion) to 10 (two equally sized groups). The formula prioritizes larger groups while accounting for the overall population size. Detailed data on both RDI and religious divide scores for all 201 countries and territories are available in appendices accompanying the report.
Researchers caution against direct comparison with the Pew Research Center’s 2014 “Global Religious Diversity” report. While the same underlying methodology is used, the religious composition data has been updated to improve comparability between 2010 and 2020 estimates. Notably, revisions to data on China resulted in a significant change to its estimated religious diversity. Adherents of folk religions are now included in the “other religions” category, reducing the number of categories analyzed from eight to seven. The updated data and methodology are outlined in the 2025 report, “How the Global Religious Landscape Changed From 2010 to 2020,” available here.
The Pew Research Center has not yet released a comprehensive ranking of countries by their RDI scores. Further analysis of the data, including regional breakdowns and comparisons, is expected in subsequent publications.
