Religious demography studies the size of religious populations and how they change over time. It offers a way to compare affiliation across traditions, alongside the study of texts, beliefs, and practices. A Pew Research Center analysis published on June 9, 2025 compares the world's religious groups in 2010 and 2020. Its publication date and the period it measures are distinct: the figures below describe 2020 and the preceding decade.
These estimates concern religious identification. They provide a demographic companion to the overview of world religions, without making a theological judgment about any group's beliefs or a judgment about the commitment of individual members.
How Religious Populations Are Counted
Pew drew on more than 2,700 censuses and surveys. Its estimates cover 201 countries and territories with populations of at least 100,000 in 2010 or 2020, together accounting for 99.98% of the world's population. Country population totals and general demographic characteristics came from the 2024 revision of the United Nations' World Population Prospects. The resulting figures are estimates assembled from demographic evidence, rather than a single worldwide register of religious membership.
Understanding the categories is as important as reading the totals. Christians of all denominations are counted together. The religiously unaffiliated are people who do not identify with any religion; Pew sometimes calls this category "nones." The category describes the absence of a religious affiliation, so it should not be used on its own to assign every person in it the same beliefs.
The "other religions" category includes Baha'is, Daoists, Jains, Shintoists, Sikhs, Wiccans, Zoroastrians, and many smaller groups, including folk or traditional religions. Combining them makes a broad demographic comparison possible, but does not make them a single religious tradition. A figure for this combined category cannot by itself show the size or direction of change of each tradition within it.
The Largest Groups
Christians remained the largest religious group in Pew's estimates, with 2.3 billion people in 2020. Their number increased by 122 million over the decade. Their share of the world's population nevertheless fell by 1.8 percentage points to 28.8%, because their numerical increase did not keep pace with global population growth. This illustrates why a rising headcount and a declining population share can occur together.
Muslims were the fastest-growing religious group over the decade, according to Pew. Their number increased by 347 million, and their global share rose by 1.8 percentage points to 25.6%. People with no religious affiliation increased by 270 million to 1.9 billion, accounting for 24.2% of the global population. The unaffiliated were the third-largest category in the study, after Christians and Muslims. This is a comparison of demographic categories, including a category defined by non-affiliation.
Steady Shares
Hindus increased by 126 million to 1.2 billion people in 2020. Their share of the world population remained steady at 14.9%, as their numbers grew at about the same rate as the global total. Jews increased by nearly one million to 14.8 million, while their global share remained about 0.2%.
The religions combined within Pew's "other religions" category also expanded in step with the world's population, retaining a 2.2% share. Here, "steady" concerns proportions rather than an absence of change in the number of people. The distinction is useful whenever a population comparison uses percentages: a similar fraction of a larger total can represent more people. Neither the size of a category nor its rate of change establishes the historical influence or religious significance of the traditions it includes.
Buddhists
Buddhists were the only major religious group in the analysis with fewer people in 2020 than in 2010. Pew estimated 324 million Buddhists worldwide in 2020, a decrease of 19 million over the decade. Their global population share fell by 0.8 percentage points to 4.1%.
This finding concerns an estimated population during a particular period. The figures alone do not explain the causes of the change, measure the intensity of Buddhist practice, or determine what will happen after 2020. Reading the result within those limits preserves the distinction between a demographic finding and a broader interpretation of a religious tradition.
Reading Demographic Figures with Care
Collectively, 75.8% of the world's people identified with a religion in 2020 in Pew's estimates, while 24.2% did not. These totals answer a question about affiliation. Questions about worship, belief, or observance require attention to what is being asked and measured; self-identification should not be treated as a measure of practice.
When comparing estimates, keep the source, reference year, coverage, and category definitions together. Estimates can differ when methods or definitions differ. A population share and an absolute count also answer different questions, while a change in percentage points should be distinguished from a percentage change. These distinctions help the reader understand what a figure establishes and what remains outside its scope.
A percentage-point change is found by subtracting one share from another. Thus, the reported 1.8-point fall in the Christian share describes the distance between two proportions; it does not say that the number of Christians fell by 1.8%. Pew's headcount moved in the opposite direction.