Global Religious Diversity Today

A report released last week from Pew Research Center, "Religious Diversity Around the World” (2026), provides a nice overview of religious diversity across 201 countries and territories. Using a modified version of the Herfindahl-Hirschman Index (HHI)—a measure economists typically use to assess market concentration—Pew constructs a Religious Diversity Index (RDI) ranging from 0 (complete religious homogeneity) to 10 (perfectly even distribution across seven religious categories).

The most religiously diverse country in the world is Singapore, with an RDI score of 9.3. No single religious tradition dominates: Buddhists (31%), religiously unaffiliated (20%), Christians (19%), Muslims (16%), Hindus (5%), and others (9%) all have significant presence. Suriname ranks second.

At the opposite end are Yemen and Afghanistan, where Muslims account for more than 99% of the population, yielding RDI scores close to 0.

A striking finding is that a single religious tradition forms a majority in 194 out of 201 countries. On the one hand, that makes it sound like religious pluralism is not quite so prevalent as might be supposed. Indeed, pluralism where no group exceeds 50% is rare, occurring in only seven countries. On the other hand, just looking at religious tradition can be misleading because there can be quite a lot of diversity in religious teaching and practices within a particular religious tradition. Just think of the Unitarian Universalists and the Amish, who both are rooted in Christianity (see the discussion on these groups in the book).

This last point is particularly relevant for the United States, whose RDI of 5.8 ties it with Nigeria as the most religiously diverse among the world's most populous countries. Although the U.S. is majority Christian (64%), nearly 30% are religiously unaffiliated, and smaller shares belong to other traditions. But keep in mind, too, that there is also tremendous diversity within Christianity in the United States, something that the RDI will not accurately account for.

The RDI is a good example of how a measurement concept that came from economics—namely the HHI—has found its way into the study of religion. However, you may be interested to know that the RDI is actually not the first time the HHI has been used to study religion, and it just takes a little internet sleuthing to find the earlier applications.

Overall, I suggest that you take away a two main lessons from this research report by Pew.

First, most of the world’s population lives in moderately diverse countries. Only 1% live in “very high” diversity contexts. This suggests that there are strong forces that drive both a degree of pluralism as well as a degree of concentration within a country. Can you think of some concepts from the book that would help to explain this fact?

Second, there is much to be gained by applying concepts from other disciplines to the study of religion. In this case, the RDI is an application of the HHI from economics, but of course there are many ideas that have come from sociology, psychology, and other fields. It is good to keep an open mind and an interdisciplinary view when studying religion.