Spread of Christianity

Determining the number of Christians around the world is a bit tricky. Any estimates that have more than two significant figures have fallen for a fallacy of misplaced concreteness. The wide variety of published estimates surely confirms this fact. Many "Christian" countries have large populations of non-practicing believers, or of non-believing practitioners. And various public opinion polls suggest that while large number of Americans may be nominally "Christian", many of them have religious knowledge that seems largely derived from Hollywood movies about angels and demonic possession.

A high-end estimate may be found at Top 10 Largest National Christian Populations, which provides data from 1997. Accepting this percentage estimate, the Christian population needs to be adjusted for the current total population. The CIA World Factbook provides recent estimates for total population, as well as somewhat lower estimates for religious affiliation. The Institute for Social Research at the University of Michigan periodically conducts the World Values Survey. This includes determining the percent of adults who attend religious services at least once a week.A survey of Percent of adults who attend religious services at least once a week provides a lower end estimate. Many polls indicate that the percentage of adults who regularly attend a religious service is about 40% in the US, 20% in Canada, and perhaps 10% or less in Europe. But when noses are actually counted, the true figures are about half the stated figures (about 20% in the U.S. and 10% in Canada.) The 50% error also appears to apply in the UK.

One of the difficulties in counting Hindus and Buddhists is that these faiths are non-congregational. Christianity is congregational, with an emphasis on fellowship, not solitude. Consequently, to be counted as a Christian would require more than simple self-identification or vague awareness of stray doctrinal tenants of faith. Christians are made, not born, unlike Muslims, who are Mulsim at birth, and for whom renouncing that faith is an apostasy punishable by death.

By one estimate, in the late 1990s about 85% of Americans were Christians, about 225,000,000 people. According the the CIA, in 2007 the American population was divided amoung Protestants 51.3%, Roman Catholics 23.9%, Mormons [!] 1.7%, and other Christians 1.6%. With a total of 78.5% identified as Christian, the mid-2012 total population of 313,000,000 would suggest of Christian population of about 245,000,000. But this number is surely too high. According to the United States Census, Christian "church adherents" were defined as “all members, including full members, their children and the estimated number of other regular participants who are not considered as communicant, confirmed or full members.” By this measure, about 133,000,000 Americans were Christians as of the year 2000.

Approximately 100 million Russian citizens identify themselves as Russian Orthodox. Many who identified themselves as members of a religious group participated in religious life rarely or not at all. Some estimates place the number of Christians in Russia at about 60%, suggesting 80,000,000 Christians, but the CIA estimates the number practicing Russian Orthodox worshipers at 15-20% of the population. But the Institute for Social Research survey indicates that only 2% of Russians are regular church-goers.

Some estimates place the number of Christians in Germany at 83%, suggesting a population of 67,000,000 Christians. The CIA counts 34% as Protestants and 34% as Roman Catholic, for a total of 68%, which with a population of 81,000,000 would suggest about 55,000,000 Christians. But the Institute for Social Research survey indicates that only 14% of Germans are regular church-goers, and given suggesting about 11,000,000 Christians. Given the two-fold over-reporting that is typical of such surveys, the actual number is probably closer to 5,000,000.

Most estimates place the percentage of the 1,300,000,000 population of China in the range of 4% to 6%. The Intitute for Social Research 9% number cannot represent Christian church attendance. According to the 2010 Blue Book of Religions, compiled by the Chinese Academy of Social Sciences' (CASS) Institute of World Religions, Christians number nearly 23 million, accounting for 1.8 percent of the population.

While some groups estimate the population to be 50 percent Muslim, 40 percent Christian, and 10 percent practitioners of indigenous religious beliefs, many observers generally assume the numbers of Muslims and Christians to be approximately equal, about 45 percent. The 89% figure cited by the Institute for Social Research survey must apply to Christian church attendance, which if applied to the CIA estimate of 40% Christians would suggest a 35% rate of actively church-going Christians out of a total population of just over 170,000,000.