For anyone expecting religion simply to disappear as education, science and technology advance, the first decades of the 21st century offer a frustrating answer.
In large parts of the developed world, secularization is real. Christianity has lost millions of adherents. More people openly identify as atheists, agnostics or religiously unaffiliated. In some countries, the transformation has been extraordinary.
Globally, however, religion is nowhere close to disappearing.
The demographic forces working in the opposite direction are enormous. Religious populations tend to be younger and, in several important cases, have more children. Meanwhile, some of the world’s most secular societies are aging and experiencing extremely low fertility.
The uncomfortable conclusion for secularists is simple: the 21st century may become more technologically advanced than anything humanity has previously experienced while remaining overwhelmingly religious.
The secular revolution is real
First, the good news for secularists.
The number of religiously unaffiliated people increased from approximately 1.6 billion in 2010 to 1.9 billion in 2020, according to the Pew Research Center’s most comprehensive recent reconstruction of the world’s religious population.
Their share of humanity increased from roughly 23% to 24%. That might look like a small change, but it occurred despite an important demographic disadvantage: religiously unaffiliated populations tend to be older and have fewer children than several major religious populations.
People are therefore actively pushing the numbers in a secular direction.
Religious switching is overwhelmingly favorable to the unaffiliated. Among adults aged 18 to 54 studied across numerous countries, for every person raised without religion who subsequently joined one, 3.2 people traveled in the opposite direction and abandoned religion.
Christianity has suffered particularly badly from this process.
For every 100 adults aged 18 to 54 who were raised Christian, Pew estimates that 17.1 have left Christianity while only 5.5 have entered it. That produces a net loss of 11.6 people through religious switching.
Those are enormous losses.
Europe is abandoning Christianity
Europe provides some of the clearest evidence that religion can lose its dominant position in a relatively short historical period.
Between 2010 and 2020, Europe’s Christian population declined by approximately 9%, falling to about 505 million.
Several countries also crossed symbolic thresholds.
Christians ceased to constitute a majority in the United Kingdom, France and Australia. The religiously unaffiliated became a majority in the Netherlands and New Zealand during the same decade.
The Netherlands joined countries and territories that were already majority unaffiliated, including the Czech Republic and Japan.
The decline was particularly dramatic elsewhere. Australia’s Christian share fell by about 20 percentage points between 2010 and 2020. Chile lost 18 points, Uruguay 16, while the United States and Canada each lost approximately 14.
These are not marginal fluctuations.
They represent a historic transformation of societies in which Christianity once exercised enormous cultural and political power.
Spain provides an extraordinary example
Spain demonstrates how quickly religious identity can change.
A remarkable 87% of Spanish adults surveyed by Pew said they had been raised Christian.
Only 54% remained Christian.
Thirty-six percent of Spanish adults had left Christianity, while only 3% had entered it. No other country included in that particular Pew analysis experienced a larger net Christian loss through religious switching.
For centuries, Catholicism was deeply intertwined with Spanish society, politics and identity.
Within several generations, that dominance has been profoundly weakened.
That is genuine secularization.
America has changed dramatically too
The United States remains much more religious than many Western European countries, but its transformation has nevertheless been extraordinary.
Pew estimates that Christians constituted 78.3% of the total American population in 2010. By 2020, that figure had fallen to 64%.
Meanwhile, religiously unaffiliated Americans increased from 16.5% to 29.7%.
In demographic terms, that is an enormous change in just ten years.
There is, however, an important warning against simply extrapolating that decline indefinitely. More recent Pew surveys suggest that the Christian share of American adults may have temporarily stabilized after decades of decline.
And there are even localized signs of revival.
Catholic dioceses in parts of the United States have reported striking increases in adult conversions in 2026. Los Angeles, for example, reported 8,598 new initiations, 54% more than the previous year. Researchers appropriately caution that one year does not establish a lasting reversal. Still, secularization should never be mistaken for an irreversible law of nature.
But religious affiliation is not belief in God
There is an important distinction here.
Being religiously unaffiliated does not necessarily mean being an atheist. A person can reject churches and organized religion while believing in God, spirituality, an afterlife or some undefined supernatural power.
Likewise, someone can identify culturally as Christian while rarely attending church and doubting fundamental Christian doctrines.
Therefore, we should not treat declining Christian affiliation as identical to declining belief in God.
What the global evidence demonstrates especially clearly is a decline in religious identification and institutional attachment across many developed societies.
That is significant in itself. But atheism has not conquered the world.
Not remotely.
Then comes the bad news for secularists
In 2020, approximately 75.8% of humanity still identified with a religion.
Only 24.2% was religiously unaffiliated.
Moreover, the secular population faces a formidable demographic problem.
The unaffiliated tend to be older and have relatively low fertility. Religion, meanwhile, remains particularly strong in parts of the world experiencing substantial population growth.
Islam provides the clearest example.
Its global expansion is not primarily being driven by masses of people converting to Islam. Switching into and out of Islam is comparatively uncommon and roughly balanced.
Instead, Muslims have a younger age structure and higher fertility, producing rapid natural population growth.
That distinction matters enormously.
You can persuade someone to abandon a religion. You cannot secularize someone who has not yet been born.
Demography therefore competes with secularization.
Christianity is shrinking and growing simultaneously
There is another apparent paradox.
Christianity is losing badly through religious switching, yet the absolute number of Christians is still enormous.
Between 2010 and 2020, the worldwide Christian population actually increased from approximately 2.1 billion to 2.3 billion.
At the same time, Christianity’s share of humanity fell from approximately 31% to 29%, because the rest of the world’s population grew much faster.
The geographical center of Christianity is also moving.
Sub-Saharan Africa has overtaken Europe as the region containing the largest Christian population.
This is one of the most important religious developments of our time.
Christianity is declining dramatically in many of the countries historically associated with it while remaining demographically powerful elsewhere.
The Christianity of the future will increasingly be African rather than European.
Secularization has a demographic problem
This produces a strange global contest.
On one side stands religious switching.
People exposed to modern education, competing worldviews, scientific explanations, greater individual freedom and weakening religious institutions frequently abandon the faiths into which they were born.
For every 100 people aged 18 to 54 who were raised without religion, the unaffiliated category gained a net 16.7 people through switching. Christianity lost 11.6 for every 100 raised Christian.
On the other side stands demography.
Many highly secular countries have low birth rates and aging populations. Some strongly religious populations are considerably younger and continue to grow rapidly.
Consequently, intellectual and cultural secularization does not automatically translate into global demographic dominance.
The secular world can win converts while losing the fertility contest.
Modernization does not automatically kill religion
For generations, a simple version of secularization theory seemed intuitively attractive.
Societies become richer.
Education improves.
Science explains phenomena previously attributed to supernatural forces.
People become less religious.
There is considerable evidence for parts of that process. Western Europe demonstrates that wealthy societies can become extraordinarily secular.
But history has refused to obey the simplest version of the theory.
The United States became one of the world’s most technologically sophisticated societies while retaining unusually high religiosity for a wealthy Western country. Wealthy Gulf states remain deeply religious. Religion remains politically powerful in India. Meanwhile, technological modernization has not prevented religious nationalism, fundamentalism or supernatural belief from flourishing.
A smartphone does not automatically produce an atheist.
Neither does a university degree.
Religion can adapt
Religion has another advantage: it evolves culturally.
Religious institutions do not have to communicate as they did in 1926 simply because their doctrines are ancient.
They use TikTok, YouTube, podcasts and sophisticated marketing. Preachers become influencers. Religious communities provide social networks, identity and belonging. Ancient beliefs can therefore travel through extremely modern distribution systems.
The current American Catholic conversion story illustrates the point. Some churches are explicitly using social media, podcasts and digital platforms to reach younger people.
Religion and technology are not natural enemies.
Technology can distribute scientific knowledge.
It can distribute superstition just as efficiently.
The 21st century will probably remain religious
So where does that leave us?
There is genuine reason for secularists to celebrate.
Christianity has suffered enormous losses in Europe, North America and parts of Latin America. Religious nones are growing. Leaving religion is substantially more common globally than moving from nonreligion into religion.
Yet declaring the imminent death of religion would be wishful thinking.
Three-quarters of humanity still identifies with a religion. Christianity and Islam together encompass billions of people. Religious populations in some of the fastest-growing parts of the world are young. Meanwhile, many highly secular societies are aging.
Perhaps the most realistic prediction is therefore neither a religious revival nor an atheist revolution.
The world may become more secular culturally while remaining overwhelmingly religious demographically.
Europe may continue losing Christianity. Parts of Latin America may follow. The United States may become increasingly unaffiliated. At the same time, Christianity may continue shifting toward Africa while Islam expands through population growth.
The sad news
For atheists and freethinkers, the decline of organized religion across much of the developed world can look like the beginning of the end.
It probably isn’t.
Humanity has landed spacecraft on other worlds. We can edit genes, build artificial intelligence and observe galaxies whose light has traveled billions of years to reach us.
Yet billions of people still organize parts of their lives around supernatural claims inherited from previous generations.
That contradiction is unlikely to disappear anytime soon.
The 21st century may be the century of artificial intelligence, biotechnology, reusable rockets and scientific achievements we can barely imagine today.
Unfortunately for those hoping humanity was about to leave religion behind, it will also remain a century of religion.
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