The world's Muslim population will grow at double the rate of non-Muslims over the next 20 years, according to a broad new demographic analysis that is likely to spark controversy in Europe and the United States.
If current trends continue, the study found, the number of Muslims in the United States will more than double, from 2.6 million in 2010 to 6.2 million in 2030. The percentage of native-born Muslims in the U.S. is projected to rise from 35 percent today to 45 percent in 2030.
The Future of the Global Muslim Population may be the first to attempt to map the Muslim population of most of the world's countries. The analysis was conducted by two giant nonprofit groups interested in religion: the Pew Research Center and the John Templeton Foundation.
Among its other projections:
l Muslim populations in some parts of Europe will reach the double digits, with France and Belgium at 10.3 percent by 2030.
l Pakistan will overtake Indonesia as the world's most populous Muslim nation.
l Muslim population growth and fertility rates will continue to decline.
The analysis could fuel critics of Islam in Europe and the United States, who argue that the religion is at odds with Western values and worry that the number of Muslim extremists is on the rise. Or it could calm those fears by providing evidence that Muslim populations in the West will remain relatively tiny.
The study - which uses a dizzying mix of public and private data sources - makes it clear that even rapid growth among Muslims will not produce dramatic demographic shifts in most parts of the world.
Eighty-two percent of the world's Muslims live in Asia, the Middle East and North Africa, and that number is projected to be around 79 percent in 2030.
According to the study's projections, Muslims make up 23.4 percent of the world's population of 6.9 billion; in 2030, that percentage will be 26.4. Europe is home to 2.7 percent of the world's Muslims, a percentage that is predicted to remain stable.
"This will provide a garbage filter for hysterical claims people make about the size and growth of the Muslim population," said Philip Jenkins, a religious history scholar known for his books on Christianity and Islam.
Yet the report's authors note that compiling even basic religious data from such a mix of divergent sources (about half of the 232 countries in the report ask about religion in their census data; for the other half researchers relied on existing private surveys) has its limitations. The report states in its opening pages that the projections "inevitably entails a host of uncertainties, including political ones. Changes in the political climate in the United States or European nations, for example, could dramatically affect the patterns of Muslim migration."
Some experts who got an advance look at the report noted a possible "us vs. them" premise - comparing a quarter of the world's population with the other 75 percent. The analysis is based on people who identified themselves as "Muslim" and includes nothing about levels of religiosity, belief or practice.
"Going into this project, that's the first question I had: 'Why are you doing this study? Are you singling out Muslims?' " said Amaney Jamal, a Princeton University political scientist who advised the project.
But Jamal said she put aside those concerns and ended up viewing as "magnificent" the project's eventual goal - mapping the world's religious populations.
Jamal said she and others who research Muslims have faced significant challenges since the Sept. 11, 2001, terrorist attacks. Whatever your area of focus or conclusion, you will be labeled "part of the fear-mongering or else you are an apologist," she said. "It's left us in a bind. The alternative is, don't try to do anything sophisticated."
John Casterline, director of the Initiative in Population Research at Ohio State University, said questions about dividing the world into Muslim and non-Muslim are inevitable. He called the framework "a crude cut" but said that didn't diminish the analysis's "very worthwhile" value.
"To say that dividing the world into Muslim and non-Muslim is the most important thing is going too far. But it's still a meaningful thing to people and to Muslims in particular. This is a very fundamental thing, people's religious identification," he said.
He noted that there are places where the number of Muslims and non-Muslims has very specific political implications, including Israel, which the analysis predicts will shift from 14 percent Muslim in 1990 to 23 percent in 2030; and Nigeria, which has seen violence between its equally sized Muslim and Christian populations.