The article seems to focus on muslim countries, not the muslims in Western Europe, where I believe they do have higher fertility rates.
Looks like the entire world, with the exception of the urban poor in the United States, is experiencing issues with an aging population. China, Japan, the muslim countries, Western Europe, the United States and Canada...
RE: Looks like the entire world, with the exception of the urban poor in the United States
Have a look at the predominantly Christian country of the Philippines... it has a fast growing economy with a birth rate of 3.1 children per family....