Islam has seen the fastest growth of any religion worldwide over the past decade, according to a major new study by the Pew Research Center.

The global Muslim population now stands at 25.6 percent, while Christians make up 28.8 percent—a decline of 1.8 percentage points for Christianity since the previous report.

Researchers say that while both faiths have grown in absolute numbers, Islam’s growth rate outpaces Christianity due to its younger demographics and higher birth rates in several regions.

Pew’s Conrad Hackett, the study’s lead author, said: “It’s just striking that there was such dramatic change in a 10-year period. Muslims grew faster than any other religion.”

Meanwhile, Christianity’s slower growth is attributed to aging populations, lower fertility rates, and rising disaffiliation, particularly in Europe and North America.

Sub-Saharan Africa now hosts the largest share of Christians globally, overtaking Europe for the first time.

The study also highlighted a sharp rise in religious disaffiliation. The unaffiliated—including atheists, agnostics, and those with no religion—now account for 24.2 percent of the global population, up from 16 percent a decade ago.

Hackett added: “Among young adults, for every person around the world who becomes Christian, there are three people who are raised Christian who leave.”

The report analyzed over 2,700 surveys and censuses from 201 countries and territories.