The Muslim population in the United States is projected to more than double in the next 20 years, from 2.6 million to 6.2 million, according to a report by the Pew Research Center's Forum on Religion & Public Life.
The estimated increase, which would put Muslims at 1.7% of the U.S. population, would be mainly from continued immigration and high fertility rates, the researchers said.
The Pew report, released Thursday, puts the global Muslim population in 2030 at 2.2 billion, about a 35% increase, which would make Muslims more than a quarter of the world's population, slightly higher than the current share.
The Pew researchers said the projected trend represented both a "growing and slowing," as Muslim population growth in the next 20 years will slow down, mostly because of declining fertility rates as more women obtain secondary education, living standards rise and more countries urbanize.
In the United States, the population increase will be accompanied by a change in the makeup of the community, both in age and national origin.
Children constitute a relatively small portion of the America Muslim community, with just 13.1% under the age of 15; most Muslims in the U.S. are newer immigrants who arrived as adults, according to the report. But as these immigrants and second-generation American Muslims start families, the number of children is projected to more than triple to 1.8 million.
The increase in the number of younger Muslims will gradually change the American Muslim community from one mainly comprising first-generation immigrants to having a more equal balance with African Americans and second- and third-generation Americans. Immigrants now make up two-thirds of the community, but over the next 20 years that percentage is expected to go down to a little more than half.
"That changes the character from being a new immigrant minority to where the parents are here and the children are here and now maybe the grandchildren are here," said Brian J. Grim, a Pew senior researcher.
Pew's current population estimate for American Muslims is far lower than the estimate of about 7 million used by the Council on American-Islamic Relations and some others. But the report's projections are largely in line with the council's expectations, a spokesman said.