The current world population is 7 billion – 1.6 billion are Muslim. Over the next 40 years, the world population is projected to increase 35 percent to 9.3 billion, according to Pew research, and of eight major religious groups calculated, only Muslims will outstrip the overall rate of population growth.
While Christians, Jews and Hindus are expected at remain at nearly the same level as the overall population – 35 percent – and Buddhists, adherents of folk religions, the unaffiliated and other religions will decline, Muslims will increase by 73 percent by 2050.
The reason for this difference, Pew found, was that on average Muslims have more children than people of other faiths. 
Muslims as a group also have a younger median age, meaning more of Muslims will soon be having children.
Also, many Muslim regions are projected to have significantly higher numbers of children than regions inhabited primarily by other religions, Pew found. While European and North American families have 2 – 2.6 children, and Asians have 2 – 2.7 children, people in the Middle East and North Africa have 2.6 – 3 children, and Sub-Saharan Africans have 4.5 – 5.6 children.
Although Muslim numbers will rise quickly in Africa and the Middle East, Pew found, the Muslim population will grow relative to the overall population in every region of the globe except Latin America and the Caribbean, where relatively few Muslims live.
By James Haleavy