Final answer:
Around 71.5% of the world's population adheres to Christianity, Islam, Hinduism, or Buddhism, with Christianity being the most widely practiced. The percentage of Buddhists could be higher than reported due to underreporting in countries like China.
Step-by-step explanation:
Approximately 71.5 percent of the world population follows a branch of the four largest religions: Christianity, Islam, Hinduism, and Buddhism. Christianity is the predominant religion with about 33 percent of people identifying as Christians. Islam has 19.6 percent adherence globally, while Hinduism is followed by 13.4 percent, and Buddhism by about 5.5 percent. However, these figures for Buddhism might be understated due to officially nonreligious countries like China, where Buddhism is widely practiced but underreported due to historical political doctrines.
Detailed demographic studies often reveal higher percentages for these religious groups when accounting for underreported populations. Other religions such as Judaism, Sikhism, Zoroastrianism, and Taoism each have less than 1 percent of global followers, and about 15 percent of people are described as non-religious.