To put those numbers into perspective, the total number of Christians globally in 2015 was 2.3 billion. The total number of Muslims in 2015 was 1.8 billion, while the religiously unaffiliated comprised 1.2 billion of the world population (Pew Research Center 2017, 8). Thus, the net impact of religious switching on demographic changes is dwarfed by the larger population growth factors of fertility rates and age distribution.

XREF: Connects to broader demography of religion literature, including Pew Research projections and growth-by-switching vs. growth-by-fertility debates.

Margaret Hodson, Baby Jihad, loc. 34