The growth of religion encompasses the expansion of individual faiths and the increasing numbers of adherents globally. In the field of sociology, the term “desecularization” refers to the resurgence or growth of religious practices and beliefs, often following a period of secularization. Statistical analyses typically focus on the absolute number of adherents, the annual growth rate, and the increase in the number of converts.

In the 21st century, research indicates that Islam is the fastest-growing major religion worldwide in terms of both percentage and geographical spread. According to a detailed forecast by the Pew Research Center, the global Muslim population is expected to grow at a faster pace than the Christian population by 2050. This projection is largely attributed to the relatively younger demographic and higher fertility rates among Muslims. Interestingly, religious conversion appears to have minimal net impact on the overall growth of the Muslim population.

It is anticipated that birth rates will be the primary driver of growth for most religions, rather than conversion. However, some scholars and sources identify Pentecostalism, a Protestant Christian movement, as the fastest-growing religion, largely due to religious conversion and denomination switching among Christians.

Accurately counting the number of converts poses significant challenges. Although some national censuses inquire about religious affiliation, they often do not ask if individuals have converted to their current faith. Furthermore, in certain countries, legal and social ramifications can make conversion difficult or even dangerous, as seen in some Muslim-majority nations where apostasy can lead to severe consequences.

Data on conversion to and from Islam are limited. A study by Pew Research in 2011 suggests that the number of people converting to Islam is roughly equivalent to those leaving the faith, indicating no significant net change in the Muslim population due to conversion.

Different religions approach proselytization in varied ways. For instance, Christianity and Islam actively seek converts, whereas Judaism and Sikhism typically do not. The growth of a religion can be influenced by multiple factors, including persecution, competition with entrenched rival religions, and market saturation. Some faiths experience rapid initial growth, particularly along trade routes or due to social prestige, only to see a decline in fervor over time, as observed in the case of Zoroastrianism.

Understanding the complex dynamics of religious growth requires a nuanced perspective that considers demographic trends, cultural contexts, and individual choices. This interfaith exploration invites thoughtful reflection on how diverse religious traditions evolve and interact in an ever-changing world.