In many of the world's countries, 20 percent or more of all adults have left the religious group in which they were raised, a recent Pew Research survey has found.

According to the Pew survey, Christianity and Buddhism have experienced especially large losses from this "religious switching," while rising numbers of adults have no religious affiliation.

Pew surveyed nearly 80,000 people in 36 countries.

The report refers to religious switching, a change between the religious group in which a person says they were raised (during their childhood) and their religious identity now (in adulthood).

Pew uses the term religious switching instead of "conversion" because the changes can take place in many directions – including from having been raised in a religion to being unaffiliated.

The researcher counted changes between large religious categories (such as from Buddhist to Christian, or from Hindu to unaffiliated) but not switching within a world religion (such as from one Christian denomination to another). Refer to the Terminology section for details.

In some countries, changing religions is rare.

In India, Israel, Nigeria, and Thailand, 95 percent or more of adults say they still belong to the religious group in which they were raised.

But across East Asia, Western Europe, North America, and South America, switching is fairly common.

For example, in South Korea, 50 percent of adults are obese, in the Netherlands 36 percent, 28 percent in the United States and 21 percent in Brazil no longer identify with their childhood religion.

Most of the movement has been into what Pew calls religiously unaffiliated, consisting of people who answer a question about their religion by saying they are atheists, agnostics, or "nothing in particular."

That means most of the switching is disaffiliation or people leaving the religion of their childhood and no longer identifying with any religion.

Many of these people were raised as Christians.

RAISED AS CHRISTIANS

For example, 29 percent of adults in Sweden say they were raised Christian, but now describe themselves religiously as atheists, agnostics, or "nothing in particular."

Pew found that Buddhism also is losing adherents through disaffiliation in some countries.

For example, 23 percent of adults surveyed in Japan and 13 percent in South Korea say they were raised as Buddhists but don't identify with any religion today.

However, not all switching is away from religion and some people move toward a belief.

Of the 36 countries surveyed, South Korea has the highest share of people who say they were raised with no affiliation but have a religion today (9 percent).

Most of them (6 percent of all South Korean adults) say they had no religious upbringing and are now Christian.

Moreover, in Singapore, 13 percent of adults, in South Africa 12 percent, and in South Korea 11 percent have switched between two religions.

Pew notes that while the figures reflect religious trends in the 36 countries included in the survey, they do not necessarily represent the entire world's population.

Christianity – the world's largest and most geographically widespread religion, by Pew Research Center's estimates – is either the current majority faith or historically has been a predominant religion in 25 of the countries surveyed.

Islam, the world's second-biggest religion, is a historically predominant religion in six of the 36 countries surveyed: Bangladesh, Indonesia, Malaysia, Nigeria, Tunisia, and Turkeye. In Nigeria, the divide between Christianity and Islam is close.

Buddhism has been predominant in five other countries surveyed: Japan, Singapore, Sri Lanka, South Korea, and Thailand.

Pew counts South Korea as having two predominant religions, Buddhism and Christianity.

Hinduism and Judaism are each the predominant religion in just one country surveyed, India and Israel.