Trends in in the Western world have show a decline in religiosity for quite some time now. While some may foresee a growing rise of secularism across the globe, these trends are not reflected in many parts of the developing world. More than 55 countries across Asia and Africa report over 90% of their populations identifying as religious. Of these nations, some tend towards religious homogeneity, whereas others are a mixed bag of diverse religious beliefs. Gauging religiosity can be complicated both by the method of investigation and the legal and social restrictions of a population. Because of this, it’s necessary to take several different approaches to measuring religiosity within a population.

Countries with 97% religious populations

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The most straightforward measure of religiosity is simply to ask populations if they identify as religious. By this measure, the third tier of supermajority religious populations is peppered across Asia and Africa. Of the countries reporting 97% religiosity, four are majority Muslim, comprising Afghanistan, Comoros, Egypt, and Morocco. Thailand, Myanmar and Laos are majority Buddhist nations, though Myanmar has no state religion.

Countries with 98% religious populations

All of the second-ranking nations by self-identifying religious practitioners are in North Africa. Of these countries, Burundi is the only majority (86%) Christian nation. Djibouti, Mauritania and Somalia also report 98% religiosity with majority Muslim populations. Mauritania reports a nearly 100% Muslim population, though religious freedom has been criticized there and may influence self-reports.

Countries with 99% religious populations

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Bangladesh, Ethiopia, Indonesia, Malawi, Niger, and Sri Lanka are the world’s most religious countries by self-identification with 99% of the population self-identifying as religious. Niger, Indonesia, and Bangladesh have supermajorities of Muslims with large celebrations and displays of their faith. Malawi and Ethiopia show majority Christian populations with a notable presence of Muslims. Finally, in Sri Lanka, Buddhism is the major religion, though it shows the most diversity among faiths in the top tier of religiosity, including adherents of Hinduism, Christianity, and Islam.

Most devout populations

Identifying as religious doesn’t necessarily equate to the devotion of adherents. Whereas religious identity is most predominant in the above listed societies, it can be separately measured as to how religious the participants in a study identify themselves. By this measure, the citizens of Israel identify most strongly with their religious identity (Jewish) among all world populations. This figure is followed closely by Muslims in Saudi Arabia and then Iran.

Largest religious populations

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The United States houses the largest number of Christians by a population of over 229 million. With 245 million followers, Indonesia has the largest number of Muslims. India is the homeland and capital of Hinduism with 957 million, and China houses the largest number of Buddhists. Finally, Israel has the largest number of Jewish citizens in the world at 6 million.

Largest religions

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Measuring by ratio and devotion is a separate measure from the size of a faith. Islam takes many of the top spots, but it is not yet the world’s most widely-practiced religion. Christianity still holds the lead in terms of followers by a substantial spread as the world’s most widely practiced religion ahead of Islam. Of the entire human population, 33% are Christian and 24.1% are Muslim. The third largest group of spiritual identity is “unaffiliated,” comprising atheists, agnostics, and the irreligious.

World’s least religious

On the opposite end of the spectrum, Sweden is among the most secular countries in the world with only 8% of Swedes regularly attending religious service, and only one in three weddings is performed by the Church of Sweden.