Islam grew from 200 million in 1900 to 1.3 billion in 2000, and is expected to further increase to 3.4 billion by 2075 (Status of Global Christianity, 2026, CSGC). The 2020-2026 annual growth rate was 1.57%, compared to Christianity’s 0.95% and the global population’s 0.86%: Islam is growing nearly twice as fast as population.
Should we then extrapolate a world that is largely or almost completely Muslim?
This is an unlikely future. Islam, for the most part, doesn’t expand by conversion–it grows principally by births. (Christianity has the twin engine of conversion and births; other world religions generally lack this.)
Since the vast majority of Islamic growth is births, “The Great Baby Bust” is rising to challenge it. And as a result, we see a form of “Peak Islam” on the very near horizon.
About two-thirds of all Muslims can be found in ten countries: Pakistan, Indonesia, India, Bangladesh, Nigeria, Egypt, Iran, Turkey, Sudan and Algeria.
About 80% of all Muslims can be found in these ten, plus 11 more: Afghanistan, Yemen, Ethiopia, Iraq, Uzbekistan, Saudi Arabia, Mali, Morocco, Tanzania, Syria, and Malaysia.
The periods of 1950-1975 and 1975-2000 saw extraordinarily high birth rates in all of these countries: for the Big 10, the populations (which were heavily Islamic, with the exception of India and Nigeria) nearly-or-more-than doubled in both periods. Pakistan, for example, went from 35 million in 1950 to 68 million in 1975, and then to 152 million in 2000.
But the two groups of countries then diverge. The Big 10 are already in the midst of their own Baby Bust. Pakistan grew by 1.9x from 1950 to 1975, and 2.23x from 1975-2000–but this fell to 1.66 for 2000-2025 and is estimated to fall to 1.46 from 2025-2050, 1.26 (2050-2075), and 1.1x (2075-2100). And Pakistan will be the exception: Indonesia’s population will fall from 278 million in 2050 to 257 million in 2100–thus, in the Big 10, the number of Muslims will be falling.
The next 11, however, are still growing and are likely continuing to do so. Afghanistan and Yemen are good examples: from 7.6 million in 1950, Afghanistan grew to 42 million now, and will on this scenario hit 128 million by 2100.
By 2100, Turkey and Iran will no longer be among the top 10 most populous Muslim countries. They will have been replaced by Afghanistan, Sudan, and Ethiopia.
Yet even in the “next 12,” the population growth rates are slowing. For the period 1950-1975, Afghanistan grew at 1.63x; by 2000-2025 it was growing at 2.14x. But the fertility crash has begun to set in. From 2025 to 2050, Afghanistan is projected to fall to 1.76x; by 2075-2100, it will be down to 1.19x.
Similar things are happening at even more pronounced rates among diaspora communities. First generation diasporas may reflect the fertility rates of their home countries (which are already declining) - second and third generation diasporas reflect the fertility rates of the country they are in, which are always dramatically lower.
AD2050, 2075, and 2100 are a long way off. Lots of things can of course change. But the important point of this analysis is that the growth of Islam is not inexorable. We are already seeing dramatic changes in birth rates of the most populous countries that directly affect the growth of Islam, along with the first fringes in the less-populous countries. Any projection of a world – or a region – that is predominantly Muslim is simply not taking the changing birth rates into account.