Related Factors: Conversion
Statistical data on conversion to and from Islam are scarce. What little information is available suggests that there is no substantial net gain or loss in the number of Muslims through conversion globally; the number of people who become Muslims through conversion seems to be roughly equal to the number of Muslims who leave the faith. As a result, this report does not include any estimated future rate of conversions as a direct factor in the projections of Muslim population growth.
Indirectly, however, conversions may affect the projections because people who have converted to or from Islam are included – even if they are not counted separately – in numerous censuses and surveys used to estimate the size of the global Muslim population in 1990, 2000 and 2010.
There are a number of reasons why reliable data on conversions are hard to come by. Some national censuses ask people about their religion, but they do not directly ask whether people have converted to their present faith. A few cross-national surveys do contain questions about religious switching, but even in those surveys, it is difficult to assess whether more people leave Islam than enter the faith. In some countries, legal and social consequences make conversion difficult, and survey respondents may be reluctant to speak honestly about the topic. Additionally, for many Muslims, Islam is not just a religion but an ethnic or cultural identity that does not depend on whether a person actively practices the faith. This means that even nonpracticing or secular Muslims may still consider themselves, and be viewed by their neighbors, as Muslims.
The limited information on conversion indicates that there is some movement both into and out of Islam but that there is no major net gain or loss. For instance, the Pew Forum’s survey of 19 nations in sub-Saharan Africa, conducted in 2009, found that neither Christianity nor Islam is growing significantly at the expense of the other through religious conversion in those countries.19 Uganda was the only country surveyed where the number of people who identified themselves as Muslim was significantly different than the number of people who said they were raised Muslim: 18% of Ugandans surveyed said they were raised Muslim, while 13% now describe themselves as Muslim, a net loss of five percentage points. In every other sub-Saharan Africa country surveyed, the number of people who are currently Muslim is roughly equivalent to the number saying they were raised as Muslims. This does not mean that there is no religious switching taking place. Rather, it indicates that the number of people becoming Muslim is roughly offset by the number of people leaving Islam.
The Pew Forum’s U.S. Religious Landscape Survey, conducted in 2007, found a similar pattern in the United States. In that survey, the number of respondents who described themselves as Muslim was roughly the same as the number who said they were raised as Muslims, and the portion of all U.S. adults who have converted either to or from Islam was less than three-tenths of 1 percent (>0.3%). Due to the relatively small number of Muslims in the nationally representative survey sample, however, it was not possible to calculate a precise retention rate for the Islamic faith in the U.S.20
An independent study published in 2010 that examined patterns of religious conversion among various faiths in 40 countries, mainly in Europe, also found that the number of people who were raised Muslim in those countries, as a whole, roughly equaled the number who currently are Muslim. But the sample sizes for Muslims were so small that the results cannot reliably predict Muslim conversion trends.21
19 Results from the survey are published in the Pew Forum’s April 2010 report Tolerance and Tension: Islam and Christianity in Sub-Saharan Africa. (return to text)
20 Because Muslims currently constitute less than 1% of the U.S. adult population, even such large studies as the U.S. Religious Landscape Survey include relatively few Muslim respondents in their representative national samples. Of the more than 35,000 respondents in the Landscape Survey, only 90 said they were raised as Muslims. That number is too small to allow reliable conclusions about the percentage of Americans who leave Islam after being raised in the faith. (return to text)
21 See Robert Barro, Jason Hwang and Rachel McCleary, “Religious Conversion in 40 Countries,” Journal for the Scientific Study of Religion, Volume 49, Number 1, pages 15-36, March 2010. This analysis of patterns of religious conversion among people age 30 and older found little evidence of a significant pattern of conversion to Islam in 40 countries where Islam is a minority religion. However, the country surveys were not designed specifically to study Muslim conversion and had too small a sample of Muslims in each country to draw firm conclusions. The most noticeable pattern of conversion across the 40 countries is movement from having some religious affiliation to having no reported religious affiliation. The cross-national surveys analyzed were conducted in 1991, 1998 and 2001. Overall, less than 1% of all the people surveyed identified as Muslim, according to the authors. (return to text)