Main Factors: Age Structure
Generally speaking, Muslim-majority countries have very youthful populations. As of 2010, people under age 30 make up about 60% of the total population of Muslim-majority countries. By contrast, only about a third of all people living in the world’s more-developed regions, such as Europe and North America, are under 30. The comparatively large number of Muslims who are in or entering their prime childbearing years is another reason for the projected growth of the world’s Muslim population.

When a country has a large percentage of people in their prime reproductive years, it gathers a kind of demographic momentum: Because many women are having babies, the population may grow rapidly even if the number of babies per woman (the fertility rate) is not especially high. Moreover, this momentum can last for generations, as the children born in one generation reach adulthood and begin having families of their own. Even when fertility rates are falling – as is the case in many Muslim-majority countries – the momentum may take more than one generation to dissipate.
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As a result of high fertility in the past, Muslim-majority countries clearly have such demographic momentum today. Women between ages 15 and 29 – those who are in or soon will enter their prime childbearing years – make up 14% of the total population in Muslim-majority countries, compared with 13% in non-Muslim-majority developing countries and 10% in more-developed countries.
More generally, people under age 30 of both sexes comprise about 60% of the population in Muslim-majority countries, compared with about 54% in non-Muslim-majority developing countries and almost 35% in more-developed countries. And Muslim-majority countries are projected to remain relatively youthful during the coming two decades. In 2030, more than 50% of the population in Muslim-majority countries is expected to be under 30, compared with almost 46% in non-Muslim-majority developing countries and almost 31% in countries in more-developed regions.
Indeed, by 2030, there will be more than 540 million Muslim youth and young adults (ages 15-29) around the world, representing nearly three-in-ten (29.1%) of the projected total of 1.9 billion people in that age group, up from 25.8% in 2010 and 20.0% in 1990.
Yet, notwithstanding the high percentage of youth and young adults in Muslim-majority countries, the global Muslim population as a whole is aging as fertility rates drop (meaning that fewer babies are born per woman) and as life expectancy rises (meaning that more people are living into old age). This is reflected in the median age in Muslim-majority countries, which has climbed from 19 to 24 over the past two decades and is projected to reach 30 in 2030.

The graph above captures the fact that the world population, as a whole, is aging. The median age – the point at which half the people in a given population are older and half are younger – is rising in Muslim-majority countries, but so are the median ages in non-Muslim-majority, less-developed countries and in more-developed countries. This explains how it is possible for the world’s Muslims to be aging and yet to remain very youthful compared with non-Muslims.
The so-called Muslim youth bulge – the high proportion of youth and young adults in many heavily Muslim societies – has attracted considerable attention from political scientists.11 Less notice has been paid to the fact that the Muslim youth bulge peaked around the start of the 21st century and is now gradually declining as the Muslim population ages. The percentage of 15- to 29-year-olds in Muslim-majority countries rose slightly between 1990 and 2000 (from 27.5% to 28.8%) but has since dipped slightly to 28.5% and is projected to continue to decline to 24.4% in 2030. While this is not a large drop, it means that the proportion of youth and young adults in many Muslim-majority countries has reached a plateau or begun to fall.

As the youth bulge moves along, the portion of the population in Muslim-majority countries between ages 30 and 44 is projected to remain fairly stable or rise slightly, from 20.2% in 2010 to 21.4% in 2030. In Muslim-majority countries, people ages 45-59 are expected to rise from 12.1% today to 16.3% in 2030.
The fastest growth of all, in percentage terms, will be among people age 60 and older, who are expected to make up 11.9% of the population in Muslim-majority countries as a whole in 2030, up from 7.3% in 2010.

Yet the percentage of the population age 60 and older will remain somewhat higher in non- Muslim-majority, less-developed countries and dramatically higher in more-developed countries, where a third of the population will be 60 and older in 2030.
Some Muslim-majority countries already have considerably older populations than others. The highest median ages at present are found in the United Arab Emirates, Kuwait, Qatar and Albania. The lowest are in Niger, Burkina Faso, Afghanistan and Chad.

In 2010, the Muslim-majority countries with the highest portion of people age 60 and older are Albania, Lebanon, Kazakhstan and Tunisia. Albania will still be at the top of the list in 2030. By that year, nearly a quarter of Albania’s population (24.0%) is expected to be age 60 or older, mirroring trends in Europe as a whole.
In 2030, the Muslim-majority countries with the highest proportion of youth and young adults (ages 15-29) will be Burkina Faso, Senegal, Sierra Leone and Mali, where about three-in-ten will be in that age group.

Footnotes
11 See, for example, Graham E. Fuller, “The Youth Factor: The New Demographics of the Middle East and the Implications for U.S. Policy,” The Brookings Institution, 2003; and Jack A. Goldstone, “The New Population Bomb,” Foreign Affairs, January/February 2010. (return to text)