If you think religion belongs to the past and we live in a new age of reason, you need to check out the facts: 84 per cent of the world’s population identifies with a religious group. Members of this demographic are generally younger and produce more children than those who have no religious affiliation, so the world is getting more religious, not less – although there are significant geographical variations.
According to 2015 figures, Christians form the biggest religious group by some margin, with 2.3 billion adherents or 31.2 per cent of the total world population of 7.3 billion. Next come Muslims (1.8 billion, or 24.1 per cent), Hindus (1.1 billion, or 15.1 per cent) and Buddhists (500 million, or 6.9 per cent).
But the third biggest category is missing from the above list. In 2015, 1.2 billion people in the world, or 16 per cent, said they have no religious affiliation at all. This does not mean all those people are committed atheists; some – perhaps most – have a strong sense of spirituality or belief in God, gods or guiding forces, but they don’t identify with or practise an organised religion.
Almost all religions have subdivisions. Christians can be Roman Catholic (the biggest group with almost 1.3 billion adherents), Protestants, Eastern Orthodox, Greek Orthodox, Anglican or many other sub-denominations.
Muslims might be Sunni (the majority), Shia, Ibadi, Ahmadiyya or Sufi. Hinduism has four main groups: Vaishnavism, Shaivism, Shaktism and Smartism. There are two main traditions in Buddhism – Theravāda and Mahayana, each with subgroups. Jews can be Orthodox (or ultra-Orthodox), Conservative, Reform or belong to smaller groups.
Geography is important in religion. Asia-Pacific is the most populous region in the world, and also the most religious. It is home to 99 per cent of Hindus, 99 per cent of Buddhists, and 90 per cent of those practising folk or traditional religions. The region also hosts 76 per cent of the world’s religiously unaffiliated people, 700m of whom are Chinese.
Three-quarters of religious people live in a country where they form a majority of the population; the remaining quarter live as religious minorities. For example, 97 per cent of Hindus live in three Hindu-majority countries: India, Mauritius and Nepal, while 87 per cent per cent of Christians live in 157 Christian-majority countries. Three-quarters of Muslims live in Muslim-majority countries. Among the religiously unaffiliated, seven out of 10 live in countries where they are in the majority, including China, the Czech Republic and North Korea.
In contrast, most Buddhists (72 per cent) live as a minority in their home countries. There are seven countries where Buddhists form the majority of the population: Bhutan, Myanmar, Cambodia, Laos, Mongolia, Sri Lanka and Thailand.