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Sources outside of Wikipedia give differing estimates:
The CIA's World Factbook gives the world population as 7,021,836,029 (July 2012 est.) and the distribution of religions as Christian 31.59% (of which Roman Catholic 18.85%, Protestant 8.15%, Orthodox 4.96%, Anglican 1.26%), Muslim 23.2%, Hindu 15.0%, Buddhist 7.1%, Sikh 0.35%, Jewish 0.2%, Baha'i 0.11%, other religions 10.95%, non-religious 9.66%, atheists 2.01%. (2010 est.).
These figures may incorporate populations of secular/nominal adherents as well as syncretist worshipers, although the concept of syncretism is disputed by some.
For Eastern religions such as Buddhism, Taoism, Confucianism, Shinto or animism etc., people often have religions which are a mix of belief systems. This leads to the unusually large uncertainty in the calculations for Buddhism. The smaller number of approximately 500 million represents traditional Buddhists (have taken refuge in the Three Jewels, those following all of the precepts of Buddhism laid down by the Buddha,) whereas the larger number of 1.2 billion includes "natural Buddhists" (as well as secular/nominal Buddhists), lacking specific ceremony, as long as they do not profess belief in another religion. Main article: Buddhism by country.
Nonreligious includes agnostic, atheist, secular humanist, and people answering 'none' or no religious preference. Half of this group is theistic but nonreligious. According to a 2012 study by Gallup International "59% of the world said that they think of themselves as religious person [sic], 23% think of themselves as not religious whereas 13% think of themselves as convinced atheists".
It is hard to accurately report the actual number of adherents of Judaism as there are Jews that do not practice the religion that may be under the secular/irreligious category even though they are fully Jewish.
Chinese traditional religion is described as "the common religion of the majority Chinese culture: a combination of Confucianism, Buddhism, and Taoism, as well as the traditional non-scriptural/local practices and beliefs."
Juche is not generally considered a religion, as it is a political belief system; some sources call it a 'political religion'.
Remarks: East Asian Buddhism is the mixture of Mahayana Buddhism, with Taoism and Confucianism. Because officially Communist governments that often forcibly suppressed religious expressions still rule a number of traditionally Buddhist countries, and because Buddhists often practice other traditional East Asian religions, the figures could be much higher in these regions. Mahayana Buddhism in Far East Asian countries has a very wide meaning. That is why in such countries as China, Vietnam, North and South Korea, Taiwan, Hong Kong, and Singapore, the three religions of Buddhism, Taoism and Confucianism are often all considered at once. This is referred to as a "Triple religion", with Gautama Buddha in the center, Laozi in the left, and Confucius in the right.
In some regions, such as Japan, belief systems vary with differing emphasis on Shintoism, as well as Ancestor Worship. Additionally, as Buddhism has harmonized with many Asian cultures, it is often regarded as a cultural background or philosophy rather than a formal religion. As such, the Buddhist population is difficult to gauge exactly, but is often nominal. The lesser percentage given is a number of Buddhists who have taken the formal step of going for refuge. And the wider percentage given are informal/nominal adherents of combined Buddhism with its related religions and those who subscribe to Buddhism and its philosophies in principle but stop short of any ceremonial or formal practice.SeeBuddhism by countryandIrreligion.
All of the below come from the U.S Department of State 2009 International Religious Freedom Report,  based on the highest estimate of people identified as indigenous or followers of indigenous religions that have been well-defined. Due to the syncretic nature of these religions, the following numbers may not reflect the actual number of practitioners.
Sources: "Most Baha'i Nations (2010)". QuickLists > Compare Nations > Religions. The Association of Religion Data Archives. 2010. Retrieved 2013-08-20. which used the "World Christian Database" for adherents estimates based on information provided by the World Christian Encyclopedia and "World Christian Trends". A source who's only systematic flaw was to consistently have a higher estimate of Christians than other cross-national data sets. See "The Largest Baha'i Communities". Largest Religious Communities. Adherents.com. 2013. Retrieved 2013-08-20. for 2000 estimates among all nations.
Remarks: Ranked by mean estimate which is in brackets. Irreligious includes agnostic, atheist, secular believer, and people having no formal religious adherence. It does not necessarily mean that members of this group don′t belong to any religion. Some religions have harmonized with local cultures and can be seen as a cultural background rather than a formal religion. Additionally, the practice of officially associating a family or household with a religious institute while not formally practicing the affiliated religion is common in many countries. Thus, over half of this group is theistic and/or influenced by religious principles, but nonreligious/non-practicing and not true atheists or agnostics. See Spiritual but not religious.
The Sikh homeland is the Punjab state, in India, where today Sikhs make up approximately 61% of the population. This is the only place where Sikhs are in the majority. Sikhs have emigrated to countries all over the world – especially to English-speaking and East Asian nations. In doing so they have retained, to an unusually high degree, their distinctive cultural and religious identity. Sikhs are not ubiquitous worldwide in the way that adherents of larger world religions are, and they remain primarily an ethnic religion. But they can be found in many international cities and have become an especially strong religious presence in the United Kingdom and Canada.
Taoists/Confucianists/Chinese traditional religionists
As a spiritual practice, Taoism has made fewer inroads in the West than Buddhism and Hinduism. Despite the popularity of its great classics the I Ching and the Tao Te Ching, the specific practices of Taoism have not been promulgated in America with much success; these religions are not ubiquitous worldwide in the way that adherents of bigger world religions are, and they remain primarily an ethnic religion. Nonetheless, Taoist ideas and symbols such as Taijitu have become popular throughout the world through Tai Chi Chuan, Qigong, and various martial arts.
The Deseret Morning News'LDS Church Almanac gives information on historical membership records of The Church of Jesus Christ of Latter-day Saints. The Church's reported membership was roughly 15,000,000 at the start of 2013.