Muslim pilgrims perform the final walk (Tawaf al-Wadaa) around the Kaaba at the Grand Mosque in the Saudi holy city of Mecca on November 30, 2009. The annual Muslim hajj pilgrimage to Mecca wound up without the feared mass outbreak of swine flu, Saudi authorities said, reporting a total of five deaths and 73 proven cases. AFP PHOTO/MAHMUD HAMS (Photo credit should read MAHMUD HAMS/AFP/Getty Images) (MAHMUD HAMS/AFP/Getty Images)

WASHINGTON (CBS DC) — Shifts in the world’s major religions will see Islam growing faster than any other faith, with the number of Muslims nearly equaling that of Christians by 2050.

A new Pew Research Center study finds that with the exception of Buddhists, the world’s major religions will all see an increase in numbers by 2050, although some will make up a smaller percentage from today. Muslims are the only major religious group projected to increase faster than the world’s population as a whole.

Over the coming four decades, Christianity will remain the world’s largest religious affiliation, but Islam will see a major increase that will make the two religions nearly equal in numbers by 2050. In 2010, Christianity was by far the world’s largest religion, with 2.2 billion followers of the faith and composing nearly one-third (31 percent) of the Earth’s 6.9 billion people. Islam was second, with 1.6 billion adherents, or 23 percent of the world’s population.

If current fertility rates and youth populations continue to grow at their current rate, Muslims will make up 10 percent of Europe’s overall population by 2050. Islam is expected to nearly match Christianity in the coming four decades as a result of a “comparatively youthful” population with high fertility rates.

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If current trends continue, Muslims will outnumber Christians worldwide around 2070.

Muslims worldwide are projected to see a 73 percent increase while Christians will rise about half that fast (35 percent). The world’s overall population is predicted to rise to 9.3 billion by 2050, also with a 35 percent rate of increase over the same time period.

In the United States, Christians will decline from more than three-quarters (78 percent) of the population to about two-thirds (66 percent) by 2050.

Muslims, “other religions” and those unaffiliated with religion will see the largest increases in North America. The religiously unaffiliated are expected to rise from 16 percent to more than one-quarter of the population, 26 percent. And by 2050, the U.S. will have more Muslims (2.1 percent of the general population) than people who identify as Jewish (1.4 percent).

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Europe is predicted to be the only region with a decline in its total population. Europe’s Christian population will see a loss of about 100 million people in the coming decades, falling from 553 million to 454 million people. Although Christians will remain Europe’s largest religious group, they are expected to decrease similarly to U.S. Christians, dropping from nearly three-quarters to less than two-thirds of the overall population.

Worldwide, Muslims have the highest fertility rate with an average of 3.1 children per woman – far exceeding the replacement level needed to maintain a stable population. Christians are second, with an average 2.7 children per woman. In 2010, more than one-quarter (27 percent) of the world’s total population was under the age of 15. And Muslims comprised an even higher percentage of this youthful group at more than one-third (34 percent), compared to 27 percent of Christians under age 15.

Pew’s “The Future of World Religions: Population Growth and Projections, 2010-2050” analysis estimates that four out of every 10 Christians in the world will live in sub-Saharan Africa by the middle of this century.

— Benjamin Fearnow