Rodney Stark says fellow sociologists scoffed when he predicted 15 years ago that The Church of Jesus Christ of Latter-day Saints could skyrocket to 267 million members by 2080.
Now he says that estimate actually may be low.He said Friday in a speech to the Mormon History Association that in the years since he made his calculations, the church has grown even faster than his highest estimate.
Stark adds that the growth has been even greater than that of early Christianity after Christ's death - which is making historians rethink early assumptions that spectacular mass conversions were needed for big boosts in membership anciently.
Stark, who is not LDS, is a professor of sociology and comparative religion at the University of Washington. He wrote a paper 15 years ago that looked at possible growth in the LDS Church between 1980 and 2080.
He made two separate calculations: one for growth of 30 percent a decade, and one for 50 percent. Both were less than the 61 percent average growth that the church had per decade from 1950 to 1980 - the three decades before he wrote his paper.
"If the low estimate were to turn out right, then there would be 60 million Mormons in 2080. If the higher estimate was met, there would be 267 million Mormons in 2080. Exponential growth really does start accelerating. Either way, we've got a very significant world movement," Stark said.
He noted such predictions "sent any number of my colleagues - and a rather surprising number of journalists - into absolute, extreme denial. But as I stand here today, it is possible to check up on the first 17 years of projections. And I'm low. The actual membership that the church reached in 1997 exceeds the high projected estimate for 1999," he said.
He says such growth is especially interesting to sociologists studying how the early Christian movement could have become as large as it did as fast as it did.
"What do we have to assume to get this (ancient) group from 1,000 members in the year 40 to about 6 million in the year 300?" Stark asked.
He said many early historians and others assumed such growth would have required mass conversions, such as "people walking into the marketplace and preaching for 15 minutes and having 3,000 people jump up and say, `We're Christians.' "
But Stark said, "I had an immense edge over other early church historians. I knew the compound interest formula. And I knew what the Mormons had done.
"And the fact is, all you have to do is assume a rate of growth of 40 percent a decade to get from 1,000 to 6.5 million in 260 years - no miracles, no mass conversions required. This is a rate considerably below what the Mormons have been doing for the last 150 years."
Stark said his studies of LDS Church growth, compared to some less successful movements, also made him rework some models of how conversion to successful, growing churches occurs and what kind of people are involved.
For example, he said, too many sociologists assume that people who promote religion do so because "they're crazy or they're crooked. Maybe both."
But he said as he watched the LDS Church and its members take care of his elderly parents, who had converted to the church in their old age, he saw them making sacrifice for the benefit of others, not personal benefit. When he asked why, he said they always told him that's what the church teaches.
"So belief matters," he said.
Also, Stark said he has observed that many new religions gain most converts among isolated people who have few personal relationships with others.
But he said LDS Church conversion isn't "based on recruitment of isolates, but on networks" of family and friends. Every convert who comes in enlarges that network and also helps increase growth.