by Tim Fang

SAN FRANCISCO (CBS SF) – While the Bay Area has one of the highest percentages of religiously unaffiliated people in the United States, a new study by the Pew Research Center projects the percentage of people belonging to a religion will go up worldwide by 2050.

Pew projects all of the major religious groups, with the exception of Buddhists, will experience growth in the next 35 years. The world’s population is projected to grow to 9.3 billion by the middle of the century.

The number of religiously unaffiliated people (atheists, agnostics and others who don’t identify with any particular religion) is expected to go up from 1.13 billion to 1.23 billion the next four decades. But researchers found the percentage of the unaffiliated is expected to drop from 16.4 percent to 13.2 percent of the world’s population.

The United States is expected to buck the trend, with the number of religiously unaffiliated rising from 16.4 percent in 2010 to 25.6 percent in 2050. Christianity is expected to remain the largest religious group in the U.S.

Pew projects Christianity would also stay as the world’s largest religious group. Meanwhile, Islam is expected to grow faster than any other major religion by mid-century, with the number of Muslims nearly equaling the number of Christians.

By 2050, Christianity will have 2.92 billion adherents (31.4 percent of the world’s population), Pew says. If trends continue, there could be 2.76 billion Muslims (29.7 percent.) The researchers cite a high fertility rate and a relatively youthful population among Muslims compared to other major religions.

Last month, the Public Religion Research Institute found 33 percent of Bay Area residents are not affiliated with any religion, tied with Seattle with the second highest percentage in the U.S. Portland, Oregon has the nation’s highest percentage of religiously unaffiliated people, at 42 percent. 

Full results of the study can be found here.