A major research institute in Washington, DC, is predicting that the global Muslim population will grow by more than a third over the next two decades - with significant increases in Europe and the United States. However, it also expects that the overall rate of growth will begin to slow down.
The report called the Future of the Global Muslim Population was prepared by the widely respected Pew Forum on Religion and Public Life.
Researchers said it is a synthesis of data from around 1,500 different sources including national censuses, health surveys and other studies. It defines a Muslim as someone who self-identifies as a Muslim, not whether he or she is secular or religious or is considered a member of the faith by religious authorities.
The Pew Forum's Associate Director of Research Alan Cooperman said one of the main findings is that the Muslim population worldwide is expected to grow at about twice the rate for non-Muslims. "So if current trends continue, Muslims will make up 26.4 percent of the world's total projected population of 8.3 billion people in the year 2030," he said.
Two of the main factors, he said, are higher fertility rates and the so-called "youth bulge." That refers to the proportionately large youthful population of Muslims who will soon enter the child-bearing phase of their lives.
But Cooperman says the actual pace of growth is slowing. "The number of children per woman has been dropping, in such countries as Indonesia and Bangladesh, as more women get a secondary education, living standards rise, and people move from rural areas to cities and towns," he said.
So he says the increase in the next twenty years will not be as large as in the last twenty years.
In America, researchers said Muslims will double in number to more 6 million in the next twenty years. That would make them as numerous as the current population of Jews or Episcopalian Protestants.
The Pew report says the Muslim share of Europe's population is expected to grow by nearly a third to 58 million.
However, researchers said there's no evidence that Islam may one day be the dominant culture in Europe. This is a prediction by the European far right known as the Eurabia hypothesis. Pew researcher Brian Grim says it is not supported by the current trend in which the Muslim share of the total European population increases by 2 percent every twenty years. "It would take many, many years. And there's no real scenario, that we've looked at, that this Eurabia scenario would come to be," he said.
One place where the Muslim population is growing fast is within Israel. Researchers said it has doubled in absolute terms since 1990, and is expected to continue to rise from around 18 percent of the total population currently to 23 percent in 2030. Grim said that is the largest percentage increase in any country in the world.