Islam: The 'Fastest-Growing' Religion?

Relative Proportion of Christianity to Islam?

(Image from Wikipedia)

We hear a lot about Islam being "the fastest-growing religion," but fastest in what sense is usually left unsaid. Islam cannot be the fastest growing in terms of percentage if compared to all religions, for some new religion with a handful of adherents might be growing by 1000 percent annually if it starts with the founder and increases in one year to 10 persons.

Indeed, I could start a new religion myself, and the growth from 0 to 1 would be statistically off the charts for the first year . . . though the growth for its second year would likely level off to, oh, about none at all.

Anyway, I think that the statement about Islam's increase can only be correct if the major world religions are being compared. But even so, does "fastest-growing" refer to percentage or to absolute numbers? And does the growth come from population expansion or from conversion?

I get all sorts of mailings in my online quest to know everything, and the following information from J. Dudley Woodberry, Russell G. Shubin, and G. Marks came just yesterday via Christianity Today:

In fact, and perhaps counterintuitively, the number of new Christians each year outstrips the number of new Muslims, even though the annual growth rate is higher for Muslims (1.81 percent) than for Christians (1.23 percent). Over the last century, Christians have grown at a slower rate than have Muslims, with Muslims increasing from 12 percent to 21 percent of the global population during that time. But this is hardly surprising. Christianity has more total followers than Islam. More people need to become Christians annually simply to remain at roughly a third of the world population. Muslims are increasing in sub-Saharan Africa and among African Americans by conversion, but elsewhere the growth is mostly by birth or immigration. The major growth for Protestants, especially evangelicals and Pentecostals, has been by conversion.

The article in which this passage occurs is titled "Why Muslims Follow Jesus: The results of a recent survey of converts from Islam" (Christianity Today, October 2007). The survey is thus only a survey of converts, specifically, 750 Muslims converts to Christianity from 30 countries and 50 ethnic groups; it is not a survey of conversion rates generally.

The information in the passage above comes from a different study that the article neglects to link to and that I haven't quickly located online though I know that I've seen it before.

At any rate -- or, actually, not at any rate -- Islam would appear to be the fastest-growing major religion if one means percentage increase, but not the fastest-growing if one means absolute increase.

Most interesting was the statement that this growth comes mostly from population expansion, not from conversion, which suggests that Islam is not actually a very popular choice among religions to convert to.

I'd like to see the hard statistics, however, and do wish that the article had linked to them.