These are among the findings discussed by religious demographer Dr Todd M Johnson in an overview of religious identity and trends in world Christianity since 1910, presented at the Ecumenical Centre, Geneva, on 13 March.
Hosted by the World Council of Churches (WCC) programme on Ecumenical Theological Education, Johnson's lecture preceded his participation in a WCC sponsored conference about the pedagogical uses of work from research centers on global Christianity.
Resurgence of several religious traditions has caused "a new wave of interest" among scholars in a variety of fields, Johnson noted, and the CSGC work is being widely cited. The CSGC holds 1 million documents and draws on censuses, polls, interviews, and religious organizations for its data on religious affiliation and trends
The CSGC's data stretches from 1910 to 2010 and fully confirm the large-scale southward shift in Christianity's center of gravity. Yet the global character of the data also yields some striking trends.
It shows that in global numbers, religious affiliation is growing, with 12 percent claiming no affiliation in 2010, versus 20 percent in 1970. Presently Christians of all sorts comprise 33 percent of the world's population, while Muslims comprise 22 percent (up from 12.6 in 1910).
Christians in the Global North comprised 80 percent of all Christians in 1910, but today make up less than 40 percent. The collapse of Chinese folk religion during the post 1949 period (from 22 to 6 percent of China's population) has been matched by the recent resurgence of religion there, significantly driving global statistics.
The data also illustrate that animist and indigenous religious traditions remain vibrant but have dramatically declined among both African and Asian populations. Africa has witnessed strong growth in Christian affiliation during the last 100 years, from 9 to 47.9 percent claiming Christian affiliation.
Migration has become a large factor in religious demographics, dramatically altering the religious make-up of some nations. The CSGC's research shows that statistics on Evangelical and Pentecostal groups are difficult to compile, since the charismatic trend goes beyond denominational affiliations.
Fastest growth over the century was seen in the category of agnostics and atheists, though both categories have been shrinking since 2000. For the first time, the rise in Christian affiliation in the Global South is outpacing its decline in the North, fueling net growth of Christianity globally.
If present trends continued, by 2050, 36 percent of the world's population would identify themselves as Christian, and by 2100 two-thirds of the world's population would be either Christian or Muslim, stated Johnson in his presentation.
He argued that while the discipline of religious demography is emergent, its initial findings about the changing landscape of global religious life pose deep questions about enculturation, theological formulation, and church organization.