There coming Harry, watch out! World Muslim population doubling, report projects â€“ CNN Belief Blog - CNN.com Blogs Twenty years ago, the world had about 1.1 billion Muslims. Twenty years from now, it will have about twice as many - and they'll represent more than a quarter of all people on earth, according to a new study released Thursday. That's a rise from less than 20 percent in 1990. Pakistan will overtake Indonesia as home of the largest number of Muslims, as its population pushes over 256 million, the Pew Forum on Religion & Public Life projects. The number of Muslims in the United States will more than double, to 6.2 million, it anticipates. Afghanistan's population will nearly double, to about 50.5 million, making it home to the ninth largest Muslim population in the world.