Q: I keep hearing different estimates being cited about how many Christians there are in Egypt. What are the facts?

A: The numbers are debated. Media reports, sometimes citing officials of the Coptic Orthodox Church, frequently say that Christians make up 10% or more of the country’s approximately 80 million people. But researchers at the Pew Forum on Religion & Public Life have been unable to find any Egyptian census or large-scale survey that substantiates such claims.

The highest share reported in the past century was in 1927, when the census found that 8.3% of Egyptians were Christians. In each of seven subsequent censuses, the Christian share of the population gradually shrank, ending at 5.7% in 1996. Religion data has not been made available from Egypt’s most recent census, conducted in 2006. But in a large, nationally representative 2008 survey — the Egyptian Demographic and Health Survey, conducted among 16,527 women ages 15 to 49 — about 5% of the respondents were Christian. Thus, the best available census and survey data indicate that Christians now number roughly 5% of the Egyptian population, or about 4 million people. The Pew Forum’s recent report on The Future of the Global Muslim Population estimated that approximately 95% of Egyptians were Muslims in 2010.

Of course, it is possible that Christians in Egypt have been undercounted in censuses and demographic surveys. According to the Pew Forum’s analysis of Global Restrictions on Religion, Egypt has very high government restrictions on religion as well as high social hostilities involving religion. (Most recently, a bombing outside a church in Alexandria during a New Year’s Eve Mass killed 23 people and wounded more than 90.) These factors may lead some Christians, particularly converts from Islam, to be cautious about revealing their identity. Government records may also undercount Christians. According to news reports, for example, some Egyptian Christians have complained that they are listed on official identity cards as Muslims.

Even if they are undercounts, the census and survey data suggest that Christians have been steadily declining as a proportion of Egypt’s population in recent decades. One reason is that Christian fertility has been lower than Muslim fertility — that is, Christians have been having fewer babies per woman than Muslims in Egypt. Conversion to Islam may also be a factor, though reliable data on conversion rates are lacking. It is possible that Christians have left the country in disproportionate numbers, but ongoing efforts by the Pew Forum to tally the religious affiliation of migrants around the world have not found evidence of an especially large Egyptian Christian diaspora. For example, in the United States, Canada and Australia, the majority of Egyptian-born residents are Christian, but the estimated total size of the Egyptian-born Christian populations in these countries is approximately 160,000. In contrast, there are more than 2 million Egyptian-born people living in Saudi Arabia, Kuwait and the United Arab Emirates, the overwhelming majority of whom are likely to be Muslims.

Most, but not all, Christians in Egypt belong to the Coptic Orthodox Church of Alexandria. Minority Christian groups include the Coptic Catholic Church and assorted Protestant churches.

Here are some sources you might want to consult for further information on the subject:

Conrad Hackett, Demographer, Pew Forum on Religion & Public Life