Eastern Orthodoxy by country
The number of members of the Eastern Orthodox Church in each country has been subject to a lot of debate. Each study performed that seeks to discover the number of adherents in a country may use different criteria, and be submitted to different populations. As such, some numbers may be inflated, and therefore inaccurate. Examples of this are Greece and Russia, where estimates of adherence to Eastern Orthodoxy may reach 80-98%, but where surveys found lower percentages professing Eastern Orthodoxy or belief in God. The likely reason for this disparity is that many people in these majority Eastern Orthodox countries will culturally identify with the Eastern Orthodox Church, especially if they were baptized as children, even if they are not currently practicing. This includes those who may be irreligious, yet culturally identify with the Eastern Orthodox Church, or for whom Eastern Orthodox Christianity is listed on official state records. Other cases of incongruent data also might be due to counting ethnic groups from Eastern Orthodox countries rather than actual adherents. A case of this is the United States, which has large numbers of immigrants from Eastern Orthodox countries. The Eastern Orthodox jurisdictions often reported large numbers of members, which together would total 2-3 million across the country. However, a 2010 study by Alexei Krindatch sought data from each parish, with the specific criteria of annual participation. This study produced the "Atlas of American Orthodox Christian Churches", and discovered that there were only about 817,000 Eastern Orthodox Christians actively practicing their faith (that is to say, attending church services on a regular basis) in the United States. The study explained that such a difference was due to a variety of circumstances, for example the higher numbers having counted all people who self-identify as Eastern Orthodox on a census regardless of active participation, or all people belonging to ethnic groups originating in Eastern Orthodox countries. This study, while initially controversial, proved groundbreaking, and has since been officially approved for use by the Assembly of Canonical Orthodox Bishops of the United States of America.
Eastern Orthodox Church
Below is a list of the 14 autocephalous Orthodox churches forming the main body of Orthodox Christianity, all of which are titled equal to each other, but the Ecumenical Patriarchate is titled the "first among equals". Based on the definitions, the list is in the order of precedence and alphabetical order where necessary, with some of their constituent autonomous churches and exarchates listed as well. The liturgical title of the primate is in italics.
Within the main body of Eastern Orthodoxy there are unresolved internal issues as to the autonomous or autocephalous status and/or legitimacy of the following Orthodox churches, particularly between those stemming from the Russian Orthodox or Constantinopolitan churches:
True Orthodoxy separated from the mainstream communion over issues of ecumenism and calendar reform since the 1920s. The movement rejects the Ecumenical Patriarchate of Constantinople, the Moscow Patriarchate, and those churches in communion with them, accusing them of heresy and placing themselves under bishops who do the same. They adhere to the use of the old Julian calendar since antiquity, claiming that the calendar reform in 1920s is in contravention of the ecumenical councils. True Orthodox writers have argued that in missionary areas such as the United States, Orthodox (SCOBA) membership numbers may be overstated, with the comparative number of True Orthodox as up to 15% of the Orthodox population, in Russia, it has been claimed by some clergy that up to a million Russians may be True Orthodox of different jurisdictions, though the total number is often cited at 1.7–2 million together.