Based on numbers, the third largest group is the religiously unaffiliated.
Four principal religions dominate the world. These four are followed by approximately 80 percent of the world’s population. These religions influence about 6.9 billion earth inhabitants. Of course there are many more religions and multiple denominations throughout the world. However, their follower numbers are much fewer. These minority religions are also found to be limited to specific geographies.
Christianity is presently the largest religion of all according to an analysis by the Pew Research Center. At the latest count made in 2015, about 2.3 billion people on earth subscribed to the Christian faith. Approximately 31.2 percent of the world’s population are Christians. The Pew Research study discovered Christianity is on a steady decline in Europe. The number of Christians are rising in Sub-Saharan Africa, North America, and Latin America.
Islam comes second with approximately 1.8 billion followers. The religion began in what is known as Saudi Arabia. Prophet Muhammad revealed its teachings to humanity. Islam followers are known as Muslims. They believe in one single God which Muslims call Allah. Among the Muslims, an overwhelming majority is Sunni (80 percent to 90 percent) and the remaining Shia (10 percent to 20 percent). Islam divided into two sects due to a dispute concerning succession post Muhammad’s death in 632 AD. About 24 percent or 1.8 billion people in the world are Muslim. The number of followers rose at a fast clip from 2010 to 2015. Births exceeded deaths by about 152 million.
The unaffiliated make up the third largest group. 1.2 billion people identify themselves “no religious affiliation.” The unaffiliated moniker is given to individuals who identify themselves as secular, agnostic, non-religious, or atheists. About 50 percent of this group are theists but not religious. Humanists are in this category as well.
Hinduism comes fourth with 900 million followers. Adherents of this religion mostly live in the Indian subcontinent. This religion is different from any other religion due to the absence of a single founder. There are many scriptures. Teachings are many and not standardized.
Buddhism comes fifth with 400 million followers.