New Survey on Global Religious Dynamics

As expected, while Islam and secularization are gaining ground, Christianity—particularly Catholicism and evangelicals—is resilient but faces numerous challenges. Between 2010 and 2020, the global religious landscape experienced significant changes, marked by contrasting demographic dynamics.

Christians – 2.3 billion in 2020, including 1.4 billion Catholics – are the largest group, representing approximately one-third of the world's population. However, their growth (+122 million) was modest, in line with overall population growth (12%). This increase is explained by a balanced geographical distribution, with a strong presence in Europe, North and South America, and sub-Saharan Africa, but also by losses due to disaffiliation, particularly in Europe.

Muslims (Shiites and Sunnis), the second largest religious group, experienced the greatest growth (+347 million), for a total of 2 billion in 2020, representing 25.6% of the world's population (+1.8% compared to 2010). This expansion is explained by high fertility rates and a young population, particularly in the Middle East, North Africa, and South Asia. The report projects that, if current trends continue, Islam could equal Christianity by 2070.

Hindus, numbering 1.2 billion in 2020, grew by 126 million, a rate comparable to that of the global population (12%). Their global share remained stable at around 14.9%, with a notable concentration in India, although their presence increased by 62% in the Middle East and North Africa, reaching 3.2 million.

In contrast, Buddhists experienced a unique decline, losing 19 million to 324 million in 2020, representing 4.1% of the global population (a decrease of 0.8%). This decline is attributed to low birth rates and an aging population in countries such as China, Thailand, and Japan, as well as notable disaffiliation in East Asia.

Another notable phenomenon of the 2010s-2020s was the number of religiously unaffiliated people, which grew by 270 million, reaching 1.9 billion in 2020, representing 24.2% of the global population (+1%). This group, which includes atheists, agnostics, and those with no religion, has grown through disaffiliation, particularly marked within Christianity and Buddhism.

Jews (15 million) and followers of other religions (Baha'is, Jains, Shintoists, Sikhs, etc.), totaling 172 million, experienced modest growth, of 7% and 12% respectively, but their share of the global population remains marginal (0.2% for Jews, 2% for other religions).

The PRC identifies three key factors explaining these changes: fertility, age structure, and international migration, as well as changes in religious affiliation. Muslims and Hindus benefit from young populations and high fertility rates, favoring sustained natural growth. Conversely, Christians and Buddhists, often present in regions with low birth rates such as Europe or East Asia, recorded slower growth or decline.

Religious disaffiliation played a decisive role. In Europe, the Christian population declined due to secularization (a 19.7% loss). Christianity and Buddhism suffered the largest net losses through conversion, while Islam and Hinduism displayed high retention rates, with only about 1% of followers abandoning their childhood religion.

International migration also influenced geographic distribution. For example, the Hindu population in the Middle East grew due to migration to the Gulf countries. In Europe, immigration helped maintain a degree of stability in the Muslim population, despite growing disaffiliation among Christians.

In Europe, the Christian population remains the majority but is shrinking, while the non-affiliated and Muslim populations are gaining ground. In Asia-Pacific (76% of the non-affiliated and 99% of Hindus and Buddhists), secularization and aging are having a strong impact. In sub-Saharan Africa, Christianity and Islam are growing rapidly, driven by high birth rates.

In summary, the first quarter of the 21st century is marked by a changing religious world, due to secularization, demographics, and migration. There is a growing trend toward disaffiliation, especially in industrialized societies, but Islam is growing thanks to its demographic vitality. Buddhists must contend with a structural decline, while Christians face the challenge of secularization, notably within Catholicism.

The PRC study has the merit of implicitly revealing that the more clearly a religion is identified, the more capable it is of attracting and shaping societies: hence the urgency for Catholicism to reclaim its Tradition.