By 2050, the number of Muslims could hit 2.7 billion — and nearly equal the number of Christians across the globe.

Four out of every 10 Christians in the world will live in sub-Saharan Africa. Jews will remain 2 percent of the world population, although their numbers will increase by 3 million.

That, at least, is the projection of the Pew Research Center’s new report, “The Future of World Religions.”

Pew found that the landscape of faiths around the globe is shifting, due largely to the fertility rates and ages of religious group members and to people switching religions.

Religions popular in developing countries with higher fertility rates are growing the fastest, the report said. Meanwhile, religions whose members are disproportionately over age 60 will see slower growth. For example, 20 percent of Jews around the world are 60 or older, compared with 14 percent of Christians and 7 percent of Muslims.

If the current trends remain, Christianity will remain the religion with the most followers in 2050, but Islam will be the fastest-growing. The number of Muslims could jump from 1.6 billion in 2010 to 2.7 billion in 2050, the report said.

The number of Christians will jump from 2.2 billion to 2.9 billion during the same period, it predicted.

Drilling down into U.S. patterns., the report says:

• Christians will drop from three-quarters of the population in 2010 to two-thirds in 2050.

• The percentage of people not affiliated with any religion will grow from an estimated 16 percent in 2010 to 26 percent in 2050.

While Christianity will remain the largest world religion, it also will see the greatest number of people leaving the faith, said the study. About 40 million people are predicted to convert to Christianity between 2010 and 2050, but 106 million are projected to leave. Most will join the ranks of “unaffiliated.”

The report is based on the assumption that current demographic, fertility and other trends will continue. Go to www.pewforum.org.