That's according to the Pew Forum on Religion and Public Life, which published on its website today projections for growth in the Muslim population between 2010 and 2030. The analysis could stoke fears among critics of Islam in Europe and America, who claim the religion clashes with Western values and spreads extremism. But it could also abate those fears, with evidence that Islam is not exploding across the globe as fast as some pundits may have suggested.
"This will provide a garbage filter for hysterical claims people make about the size and growth of the Muslim population," Philip Jenkins, a religious history scholar known for his books on Christianity and Islam, told The Washington Post.
According to the Pew report, the total number of people who identify themselves as Muslims is currently about 1.6 billion. That figure is expected to rise to 2.2 billion by the year 2030. That's an average growth rate of 1.5 percent, compared with forecast growth of 0.7 percent for non-Muslims over the next 20 years. If those trends continue, Muslims will make up 26.4 percent of the world's population in 2030, compared with 23.4 percent now.
While today's findings don't include information on the growth rates of other religious groups, other sources have estimated the world's Christian population to be 30 percent to 33 percent. Pew said it plans to release similar reports on the growth of worldwide Christianity, Hinduism, Buddhism, Sikhism and Judaism.
Today's figures show the rate of overall growth in the world's Muslim communities is slowing. As more Muslim women go to school longer and join the workforce, and as people move to cities and living standards improve, the birth rate among Muslims is forecast to drop -- approaching that of non-Muslims.
"The increase in the last 20 years is greater than what we expect in the next 20 years," Pew's associate director, Alan Cooperman, told CNN. He said Muslim population growth "is a line that's flattening out. They're increasing, but they're getting closer to the norm, the average."
Thus, any predictions that Europe may in the future become "Eurabia," with a majority Muslim population, don't pan out.
"There's this overwhelming assumption that Muslims are populating the Earth, and not only are they growing at this exponential rate in the Muslim world, they're going to be dominating Europe and, soon after, the United States," Amaney A. Jamal, an associate professor of politics at Princeton and a consultant for Pew on global Islam, told The New York Times. "But the figures don't even come close. I'm looking at all this and wondering, Where is all the hysteria coming from?"
According to the Pew report, 6 percent of Europeans are Muslim today, a proportion that's expected to rise to 8 percent by 2030. In France and Belgium, the numbers are a bit higher -- forecast to hit 10 percent in 20 years. Britain will have the same average percentage as the continent -- 8 percent.
In the United States, the number of Muslims is expected to double over the next 20 years, to 6.2 million. The proportion of U.S.-born Muslims in America is projected to rise from 35 percent to 45 percent over that period.
Overall, Pakistan will overtake Indonesia as the home of the largest number of Muslims, with a population forecast to top 256 million over the next two decades.
But one Muslim country that's expected to see very slow population growth is Iran, which has the lowest birth rate of any country in the Islamic world. Iranian women use birth control at exactly the same rate as Americans, about 73 percent.