Pew Research Center – Why Muslims Are Rising Fastest and the Unaffiliated Are Shrinking as a Share of the World’s Population – “The religious profile of the world is rapidly changing, driven primarily by differences in fertility rates and the size of youth populations among the world’s major religions, as well as by people switching faiths. Over the next four decades, Christians will remain the largest religious group, but Islam will grow faster than any other major religion. If current trends continue, by 2050..

• The number of Muslims will nearly equal the number of Christians around the world.
• Atheists, agnostics and other people who do not affiliate with any religion – though increasing in countries such as the United States and France – will make up a declining share of the world’s total population.
• The global Buddhist population will be about the same size it was in 2010, while the Hindu and Jewish populations will be larger than they are today.
• In Europe, Muslims will make up 10% of the overall population.
• India will retain a Hindu majority but also will have the largest Muslim population of any country in the world, surpassing Indonesia.
• In the United States, Christians will decline from more than three-quarters of the population in 2010 to two-thirds in 2050, and Judaism will no longer be the largest non-Christian religion. Muslims will be more numerous in the U.S. than people who identify as Jewish on the basis of religion.
• Four out of every 10 Christians in the world will live in sub-Saharan Africa.”