Benjamin Fearnow, CBS Washington, April 2, 2015

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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.

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.

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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. {snip}

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. {snip}

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.