Immediately after 9/11, many journalists in the United States and Europe came out with several glib generalisations that I found, and still find, irritating, and furthermore, I am very skeptical of the claims contained in them. We were told that either 40,000  or even 60,000 people had converted to Islam in the wake of the attacks on the Twin Towers in Manhattan, and that Islam was the fastest growing religion in the world. The figures 40,000 and 60,000 come up time after time. A quick Google search will give you many journalists evidently copying each other without any verification or independent evidence. For example, author Ed Rogers, writing in 2009, tells us that “…60,000 Americans who were raised in a “Christian” home are converting to Islam every year” .
But this turns out to have been copied without acknowledgement from a book written in 2004 by Joel Richardson, Will Islam Be Our Future? A Study of Biblical and Islamic Eschatology, Chapter 1: “But here’s the other sad aspect of these figures: Over 80% of these American converts to Islam were raised in a Christian Church. If the higher figures of conversion are accurate, that would mean that as many as 60,000 Americans, who were raised in Christian homes, are converting to Islam annually.”  So now the figure 60,000 is claimed for annual rates of conversion.
Another report, published in 2011 by the Religion News Service, based in Boston, tells us, “The majority of post-9/11 converts are women, according to experts, Hispanics and African-Americans, who were already converting well before 9/11, are the most common ethnic groups to convert. Though exact numbers are difficult to tally, observers estimate that as many as 20,000 Americans convert to Islam annually”. Notice, first, the new figure for the number of annual converts: 20,000, and, second, those ubiquitous “experts”, but we are not told which “experts” or how they have made their calculations. They are now joined by “observers”. 
Another quote that comes up over and over again is from The Times of London, January 7, 2002: “There is compelling anecdotal evidence of a surge in conversions to Islam since September 11, not just in Britain, but across Europe and America. One Dutch Islamic centre claims a tenfold increase, while the New Muslims Project, based in Leicester, [England] and run by a former Irish Roman Catholic housewife, reports a “steady stream” of new converts.”
“Anecdotal evidence” in the form of personal testimonies can be powerful, moving, and very useful, though one has to treat such evidence with caution when trying to calculate national number of converts. As for the number of Muslims in the United States, there have often been unscientific guesses, with many Muslim organizations inflating their figures for political reasons. As Dr Tom W. Smith of the University of Chicago wrote in October 2001, “None of the 20 specific estimates during the last five years is based on a scientifically-sound or explicit methodology. All can probably be characterized as guesses or assertions. Nine came from Muslim organizations such as the Islamic Society of North America, the Muslim Student Association, the Council on American-Islamic Relations, the American Muslim Council, and the Harvard Islamic Society, or unspecified ‘Muslim sources.’ None of these sources gave any basis for their figures.” 
Certainly the most sober assessment of numbers and conversions seems to come from The Economist. In an article published in 2013, The Economist cites the research of Kevin Brice, of the University of Wales, who calculated that 5200 Britons convert to Islam every year, and that the total number of converts is about 100,000; presumably over a period of twenty years, though this is not made clear. For the United States, The Economist turns to the Pew Research Center, and says: “In 2007 the Pew Research Centre (sic) estimated that there were around 2.4 million American Muslims…Pew reckons that just under a quarter are converts”. Actually, the Pew Research Center did no such thing. First, The Pew Research Center only gives percentage estimates, and second, they are for adults only, children are not included.
According to The Pew Research Center, basing themselves on the Religious Landscape Study [RLS], Muslims made up 0.4 % of the adult population in 2007.  How did The Economist arrive at the figure of 2.4 million Muslim Americans? According to the Pew Research Center, in 2007, there were 227 million adult Americans , in which case, 0.4% of them were Muslim Americans, that is, 908,000. And the adult population of the USA in 2014 was approximately 245 million, of which 0.9% were Muslims, that is, 2,205,000.
Thus there was a net increase in Muslim American adults of 1,297,000 over a period of seven years, that is, 185,285 per annum. How many of these are a result of conversion remains obscure, since the figure of 185,285 must take into account the number of Muslim immigrants per year. We have yet to factor in the rate of retention, that is, the percentage of people raised in a particular church or religion who stay with it when they are grown. For Muslims it is high, 77 %, but that still means that 23% of Muslim adults lose their religion.  I have no idea of the implications of this statistic, and how it would affect the numbers of Muslim Americans.
However, to complicate things further, in the second paragraph on page 28 of their 2014 Religious Landscape Study [RLS], the Pew Center explains: “Muslims (0.9%), Buddhists (0.7%) and Hindus (0.7%) each make up slightly less than 1% of respondents in the 2014 Religious Landscape Study. The Muslim and Hindu shares of the population have risen significantly since 2007. And it is possible, even despite this growth, that the Religious Landscape Study may underestimate the size of these groups. The study was conducted in English and Spanish, which means that groups with above-average numbers of people who do not speak English or Spanish (such as immigrants from Asia, Africa and other parts of the world) may be underrepresented. For instance, an analysis of the Pew Research Center’s 2012 survey of Asian Americans (conducted in English, Cantonese, Hindi, Japanese, Korean, Mandarin, Tagalog and Vietnamese) estimated that Buddhists account for between 1.0% and 1.3% of the U.S. adult population, and that Hindus account for between 0.5% and 0.8% of the population. The Pew Research Center’s 2007 and 2011 surveys of Muslim Americans (conducted in English, Arabic, Farsi and Urdu) estimated that Muslims accounted for 0.6% of the adult population in 2007 and 0.8% in 2011.”  Thus based on the latter figures, 0.6% of the total adult population of 2007, which was 227 million, gives us a figure of 1,362,000 adult Muslim Americans. The total adult population in 2011, according to the U.S. Census Bureau , was 237,680,342, of which 0.8% were adult Muslim Americans, giving us the figure of 1,901,443 adult Muslim Americans. Thus there was an increase of 539,443 Muslim American adults between 2007 and 2011, an increase of approximately 134,860 per year.
The Pew Research Center gave the following figures for converts in 2007:
More than three-quarters (77%) of Muslim Americans say they have always been a Muslim, while 23% say they converted to Islam. Nine-in-10 (91%) converts to Islam were born in the United States, and almost three-fifths (59%) of converts to Islam are African American.
A 55% majority of converts identify with Sunni Islam and another quarter (24%) identify with no specific tradition. Only 6% of Muslim converts in America identify themselves as Shia.
Almost half (49%) of Muslim converts in America report that their conversion occurred when they were under 21 years of age, another third (34%) converted when they were between ages 21 and 35, and 17% when they were older than 35. The early age of most conversions to Islam resembles the typical pattern of conversion in the general public, where religious change is concentrated in adolescence and early adulthood.
Two-thirds (67%) of all converts to Islam in the U.S. came from Protestant churches,10% came from Catholicism, and just 5% from other religions. Nearly one-in-seven converts to Islam (15%) had no religion before their conversion.
Most converts to Islam (58%) cite aspects of the religion as the reason for their conversion. These include references to the truth or appeal of Islam’s teachings, the belief that Islam is superior to Christianity, or that the religion just “made sense” to them. Just 18% of converts mentioned family reasons, such as marrying a Muslim, as the reason for their conversion. 
Thus, as we saw earlier, if we take the adult population of Muslim Americans as 0.6% of the total adult American population of 227 million in 2007, that gives us a figure of 1,362,000 adult Muslim Americans. Now 23% of these Muslim Americans are converts; that gives us a figure of 313,260. However, the Pew Research Center’s 2011 study of Muslim Americans tells us that only 20% are converts. As we saw earlier, the total adult population in 2011, according to the U.S. Census Bureau, was 237,680,342, of which 0.8% were adult Muslims, giving us the figure of 1,901,443 adult Muslim Americans. If 20% are converts, we get a figure of 380,288 Muslim Americans converts in 2011.
That comes to an increase of 67,028 converts since 2007, that is, 16,757 new converts to Islam per year. So where do those mysterious figures of 60,000, or 40,000, or even 20,000 annual converts to Islam that we read about in the press come from?
Hispanics have also converted to Islam in recent years. There are, perhaps, between 15,000 and 50,000 Hispanic Muslims in the United States — exact figures are hard to come by, and Muslim groups, as ever, exaggerate the numbers. The majority of Hispanic converts to Islam are women.  But as the Washington Report on Middle East Affairs concluded, “Despite the growing presence of organizations such as Alianza Islamica, however, Latino Muslims are still a tiny fraction of the Latino population. Few Latinos, in fact, are even aware of their existence.” 
But here are some sobering statistics for Muslim triumphalists:
1. According to Dr. Ilyas Ba-Yunus (1932-2007), a Pakistani-born American Muslim and Emeritus Professor of Sociology, State University of New York at Cortland, 75% of new Muslim converts in the US leave Islam within a few years.  This perception was confirmed by Imam Abu Laith Luqman Ahmad, who wrote on January 13, 2010:
We are constantly being told that Islam is the fastest growing religion in the United States. We are also being told that the Muslim population is anywhere from 2 million, to six million and that a third of them are converts. That would put the number of converts from around 700,000 to 2,000,000. However, I’m not sure if those numbers are accurate because many converts are leaving Islam, and or never even begin to practice Islam in any appreciable way other than take their shahaadah (declaration of conversion), and you don’t see anywhere near those numbers reflected in the nation’s masaajid [mosques]. Nor do you see too much evidence that people who became Muslim say, 20 years ago have stayed in the religion, raised their children upon it and started a second generation, or even third generation. The overall estimates of the Muslim population may be accurate, but the stated percentage of converts does not seem reflected on the ground. In almost every major city in America except for maybe Philadelphia and to a certain extent, Atlanta, you don’t see too many large communities of converts to Islam. You see a lot of young people who are recent converts and that’s great but where are the thousands upon thousands of Muslims who converted ten years ago? Twenty years ago? Thirty years ago? Where are their children, their grandchildren? We need to re-evaluate the statistics that are being fed to us, because it has lolled many of us into a false sense of accomplishment to the point where we brag about how well Islam is doing amongst converts in America while in reality, it seems converts, by and large, are not faring that well and that the largest concentrations of Muslim men in America are those in our nation’s prisons. When I used to volunteer at Folsom prison, there would be hundreds of male converts in attendance, and I have never seen hundreds of male converts at any Masjid anywhere in California. 
2. Further evidence of converts leaving Islam comes from a London-based think tank. The British journal The New Statesman cites Usama Hasan, a part-time Imam and a senior researcher at the “counter extremism think-tank,” the Quilliam Foundation, as saying, “Many converts leave the faith. We don’t have exact statistics but some stats say 50 per cent will leave within a few years”. 
3. Roughly two-thirds (65%) of adult Muslims in the U.S. were born elsewhere. A relatively large proportion of Muslim immigrants are from Arab countries, but many also come from Pakistan and other South Asian countries. Among native-born Muslims, roughly half are African American (20% of U.S. Muslims overall), many of whom are converts to Islam. 
4. According to Ahmed Nassef, the co-founder and editor in chief of MuslimWakeUp.com, fewer than 7 percent of American Muslims attend mosque regularly, compared with 38 percent of American Christians who attend church weekly. 
5. Contrary to Islamic claims, the fastest growing belief groups in the United States are the non-religious. The American Religious Identification Surveys [ARIS] of 1990 and 2000 show that the percent of change for Islam was +109%. The percent of change, however, for Nonreligious/Secular was +110%; Native American Religion +119%; Buddhism +170%; Baha’i +200%; Hinduism +237%; New Age +240%; Sikhism +338%, and Deism +717% were all higher. 
6. The American Religious Identification Survey [ARIS] gave Non-Religious groups the largest gain in terms of absolute numbers – 14,300,000 (8.4% of the population) to 29,400,000 (14.1% of the population) for the period 1990 to 2001 in the USA.
7. In the period from 2001 to 2008, Americans with no religion were the fastest-growing segment.  There were sharp increases in the number of non-denominational Christians and those claiming no religious affiliation (Nones). To quote the report from ARIS’ webpage:
In addition, shifts in religious identification since 1990 have resulted in the ranks of the Nones swelling by 67 percent (2.2 million persons) and those in the conservative, non-denominational Generic Christian tradition growing by 51 percent (1.8 million). Put another way, the percentage of self-proclaimed Nones increased from 11 percent to 16 percent of this cohort between 1990 and 2008. This increase is surprising since Americans have historically increased their religious identification between early adulthood and their mid-40s, as they marry, have children, and become settled in their communities.
8. The true rate of Muslim apostasy in the United States is difficult to assess for the obvious reason that though there are no laws prohibiting it, social ostracism, feelings of shame, and simple physical fear of reprisals even in the West all conspire to make the apostate keep his own counsel.
9. Here is the ever-sober Pew Research Center’s assessment on 27 January, 2011:
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. 
10. What are the difficulties in estimating conversions to and from Islam?
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. 
11. However, some more recent research suggests the Pew Research Centers assessments are incorrect, and that there are greater conversions from Islam to Christianity, or other religions, and even atheism, than have been reported. Admittedly, much of this research has been conducted by Christian organizations but, as I shall show, at least some of these Christian organizations have developed and used a sophisticated methodology that promises some more objective facts and figures than mere crude propaganda. To take an example of what can go wrong, let us look at one Christian reference work. Referring to its own massive charts and statistics, the three-volume The World Christian Encyclopaedia, published by Oxford University Press, estimates that between 1990 and 2000, Islam received around 865,558 converts each year. This compares with an approximate 2,883,011 converts each year for Christianity during the same period.  But to show my skepticism of even Christian sources, I refer readers to the criticisms levelled at the three volumes, comprising more than 1730 pages, by Glenn Masuchika of Chaminade University Library, Honolulu. He thinks that volume two is the most useful, but adds that it
suffers from the shadow of doubt cast by the first volume concerning the reliability of the encyclopedia’s facts. Volume 3 can be best described as an explosion of numbers, categories, cross-listings of what the editors define as ‘miniprofiles’ of at least 10,000 distinct religions, 12,600 peoples, 13,500 languages, 7000 cities, and 3030 major civil divisions in 238 countries. What results is hundred of pages of utterly confusing statistics, some highly suspect, culturally biased, and anthropologically useless (such as categorizing people by using moribund race-defining terms as Australoid, Negroid, and Mongoloid and further subdividing those into “stylized colors” such as black, grey, brown, red, tan, white, and yellow). There is a need for a comparative survey of world Christian churches and other religions. This is not it. Not recommended. 
PART TWO: CONVERSIONS TO CHRISTIANITY.
In the last fifteen years, there has been a spate of books, published in the West, by Muslims who have converted to Christianity, and many anthologies of testimonies of former Muslims. The internet, of course, is full of Christian sites with the testimonies of former Muslims.  These personal journeys, some moving and some very sentimental, are of considerable interest, but do not help us to establish the number of true conversions to Christianity in the Islamic world. Large claims are made by various Christian evangelical groups giving suspect statistics.
I remember being startled when I came across an article in the French journal Courrier International of January 4-10, 2001, page 29. The latter journal, in turn, was translating an article that first appeared in the Algerian daily newpaper Al-Yawm in late December 2000. I translated it for The Middle East Quarterly.  The article begins:
In Kabylie, people of all ages are converting to Christianity. In certain towns and villages of Greater Kabylie, there is at least one church, as for example at Ouadhias, Draa Benkhedda, Ain el-Hammam, and Boghni. In the latter village, for instance, two churches have opened their doors during the last two years. Although the original builders of these two churches had worked in absolute secrecy, the number of citizens who have embraced Christianity has grown rapidly. The [Protestant] church of Ouadhias has played an important role in the proliferation of the number of conversions in Kabylie, and it is considered the Mother Church, never having ceased its activities, even after [Algeria’s] independence  and the departure of the French and humanitarian missionaries.
This was credible since it appeared in an Algerian newspaper, and startling since Algeria at the time was undergoing a civil war of unbelievable savagery that resulted in the deaths of perhaps as many as 200,000 Algerians.  Women had their throats cut for wearing lipstick, and yet here were Muslims converting to Christianity, and risking a similar fate.
Many of the converts were Berbers or Amazigh who are an ethnic group indigenous to North Africa; most now live in Algeria (in the Kabylie region) and Morocco but are also to be found in Tunisia, Libya, Mauritania, Mali and Niger. They speak their own language, and have in recent years tried to reclaim their pre-Islamic Berber culture and identity, and resent being called “Arab”. The main opposition political parties in Algeria are secular and mainly Berber.
Twelve years later, we find the following report (13 November 2012) in the Arabic online journal Ilaf [Elaph]  on the continuation of Algerians, including many Berbers, converting to Christianity, with the words: “That Algerians are leaving Islam is a phenomenon not denied by the government or civil organizations; however it suffers from being a subject not openly discussed. Added to that, is a paucity of documented information necessary for a proper pursuit of our investigation.”
The report then tells us:
The subject of Christianization remains a much discussed matter in Algeria, even though no official census exists that would reveal the actual number of people who have embraced Christianity. Neither the Ministry of Religious Affairs & Awqaf nor the Algerian Episcopal authorities are willing to divulge their number. While governmental authorities tend to minimize the size of this phenomenon, discussion of it is occurring among both politicians and religious leaders regarding its spread among Algerians, especially among the young people.
According to the field research of three Algerian experts, Jalal Mousa, Salaf Rahmouni, and Naseema Raqiq, there is a noticeable rise in the number of Algerians leaving Islam, reaching 10,000 people, and averaging six individuals per day, most of whom are young people. According to researcher Jalal Mousa, “the number of people who have embraced Christianity is estimated at 10,000.”
In his research, Mousa emphasized that “those becoming Christian move freely without any governmental surveillance, and in turn, concentrate their efforts on working among the young people, with the goal of establishing a religious minority who are willing and active in defending their rights. Their activities are accomplished through philanthropic organizations that seek to prevent young people from indulging in the use of alcoholic beverages and narcotics, and calling them to adopt good morals.”
According to some experts, the Grand Kabyle region has become a fertile field for evangelization by Western Christians who often visit the area. Nineteen Christian philanthropic organizations are also active, making a claim of an average of 6 converts per day.
The U. S. Bureau of Democracy & Human Rights of the Department of State estimates that the number of non-Muslims in Algeria has reached 500,000. They attend 300 churches, most of which are in the Kabyle region. 
Again, this is a report from an Algerian online news service, and cannot be easily dismissed as Christian propaganda.
Amazigh (Berber) self-assertion has increased in recent years, and is a positive sign. As Berber specialist Bruce Maddy-Weitzman put it:
There is even a body called the World Amazigh [Berber] Congress, established in 1997 and headquartered in Paris, that brings together constituent associations in periodic gatherings. And even as they decry the perfidious, leveling impact of globalization processes on indigenous cultures, Amazigh activists have enjoyed the benefits thereof, maintaining an active presence in the cyber-world …. There they come into partial alliance with other “civil society” forces such as the women’s and human rights groups and the liberal political voices and bloggers of North Africa’s overwhelmingly youthful population.
A further indication of this outward-looking, modern perspective is the fact that the movement’s overarching discourse is profoundly sympathetic to Western liberal-humanist values and strongly condemns the predominant North African political and cultural order, which prioritizes Islam and Arab identity in an uneasy and erratic coexistence with French linguistic and cultural influences. As such, the Amazigh movement leaves little or no room for other, more Islamic-centered aspects of Berber societal norms. This may well prove to be a serious shortcoming in Amazigh mobilization efforts, but to the extent that those efforts succeed, Amazighité represents a bulwark against the spread of Islamist influence. 
As Mira Z. Amiras also explains, “Amazigh militants reject both Islam and Arabism, claimimg that Islam is nothing more than a mask for Arabism rather than the reverse”.  I shall discuss the assassinated Amazigh or Berber Kabyle singer and human rights activist, Lounès Matoub, who was an atheist, later, under the section Muslim atheists.
 See, for example: https://yesuscross.wordpress.com/category/tv-report-40000-catholic-hispanics-in-america-converted-to-islam-after-911/
 Omar Sacirbey in Religion News Service Boston, 08/24/2011, found at http://www.huffingtonpost.com/2011/08/24/post-911-islam-converts_n_935572.html
 Full Report: http://www.pewresearch.org/files/old-assets/pdf/muslim-americans.pdf, page 28
 National Public Radio Report by Rachel Martin, “Latinas Choosing Islam over Catholicism”: http://www.npr.org/templates/story/story.php?storyId=6133579 ”
See also a report in Washington Report on Middle East Affairs at: http://www.wrmea.org/2003-june/latino-muslims-a-growing-presence-in-america.html.
 Washington Report on Middle East Affairs at: http://www.wrmea.org/2003-june/latino-muslims-a-growing-presence-in-america.html.
 Regrettably, the original YouTube video where Dr Ba-Yunus stated the figure “75%” is no longer available. Some who heard him speak talk of “50%” or “60%” of Muslim converts leaving Islam after a few years. See Islamic Research Foundation International, Inc. at: http://www.irfi.org/articles4/articles_5001_6000/why%20muslims%20in%20the%20west%20leave%20islam%20and%20what%20can%20we%20do%20about%20ithtml.htm
 Pew Research Center, Muslim Americans: Middle Class and Mostly Mainstream (Washington, DC, Pew Research Center: 2007)
 Press: Generation X Becoming Less Christian, Less Republican; Catholic and Baptist Losses feed Religious Polarization, May 31, 2012, at http://commons.trincoll.edu/aris/
 http://www.bible.ca/global-religion-statistics-world-christian-encyclopedia.htm&date=2011-04-16, citing David A. Barrett, George Thomas Kurian, Todd M. Johnson, edd., World Christian Encyclopedia, 2001, Oxford University Press, p 16-18.
 Glenn Masuchika, Review of The World Christian Encyclopaedia in Library Journal, May 1, 2000.
 Here is a random list of ten:
Joel Richardson and Susan Crimp. Why We Left Islam: Former Muslims Speak Out, WND Books; 1 edition (April 29, 2008).
Steve Mashni, Out of Darkness Into Light: True life stories of Muslim’s Coming to Jesus Christ Through Visions, Dreams and Miracles, Kindle Edition, 2015
Robert Hussein, Apostate Son, Najiba Pub Co; 1st edition (December 23, 1998)
Ant Greenham, Muslim Conversions to Christ: An Investigation of Palestinian Converts Living in the Holy Land , William Carey International University Press (January 11, 2011)
Ergun Caner &, Emir Fethi Caner. Unveiling Islam: An Insider’s Look at Muslim Life and Beliefs, Kregel Publications; Updated and Expanded edition (April 14, 2009)
Bilquis Sheikh, I Dared to Call Him Father: The Miraculous Story of a Muslim Woman’s Encounter with God, Chosen Books (April 1, 2003)
Nabeel Qureshi, Seeking Allah, Finding Jesus: A Devout Muslim Encounters Christianity , Zondervan (February 11, 2014)
Samaa Habib &, Bodie Thoene ,Face to Face with Jesus: A Former Muslim’s Extraordinary Journey to Heaven and Encounter with the God of Love Chosen Books, June 3, 2014
Gulshan Esther, The Torn Veil , CLC Publications (November 1, 2010)
 “Christianity Is Life”, Middle East Quarterly, Summer 2001, pp. 94-95. Available at http://www.meforum.org/104/christianity-is-life
 Fouad Ajami (January 27, 2010). “The Furrows of Algeria”. New Republic.
 Jacob Thomas, The Christianization of Algeria, published 2013 at http://www.answeringislam.org/authors/thomas/christianization_algeria.html
 Bruce Maddy-Weitzman, “The Berber Awakening” in The American Interest, Volume 6, Number 5 : May 1, 2011.
 Mira Z. Amiras Amazighité, Arab/Islamic Hegemony,and the Christian Evangelical Challenge, in edd. Galina Lindquist & Don Handelman, Religion, Politics and Globalization Berghahn Books, 2011, p.226.