RICHMOND, Va. -- When Britain's Royal Aircraft Establishment reassigned David B. Barrett from airplane design to missiles and warheads in 1952, it became a turning point -- and not just for him.
The aeronautical engineer quit to train for the Church of England priesthood, expressing hope the church could make use of his mathematics expertise and pioneering computer work.
"Forget science completely," his bishop advised. But Barrett could not.
Since adding a religion doctorate from Columbia University to his technical background, he has spent 40 years systematizing information on world religions, a calling he discovered while assigned as an Anglican missionary in Africa.
Now 73, Barrett recently culminated his oddly remarkable career with publication of the second edition of his global accounting of faiths and the faithful -- trends, details and his best estimated count of believers of all religions in each of 238 nations and territories.
Never has there been such a thorough reference as the two large volumes, running 1,699 pages, of the World Christian Encyclopedia, published by Oxford University Press.
Barrett has doggedly visited most of the lands in person, collecting raw material, including national census figures and United Nations data, and recruiting the 444 specialists who feed him material. Among them: Vatican missions librarian Willi Henkel and editor J. Gordon Melton of the Encyclopedia of American Religions.
Barrett's encyclopedia sought to count each human being in each religion and religious subcategory in each country as of 1900, 1970, 1990, 1995 and 2000, with projections to 2025.
The 2001 edition, successor to his 1983 first edition, which took a decade to compile, identifies 10,000 distinct religions, of which 150 have 1 million or more followers. Within Christianity, he counts 33,830 denominations.
Barrett also calculates religious populations for the Encyclopedia Britannica Book of the Year, standard estimates that are used in turn by the World Almanac and innumerable journalists.
Such numbers are always debatable, but they're the best available. "We don't really have any rivals," Barrett says. "That's the problem."
Why the title World Christian Encyclopedia, when it covers faith groups from Afghan Zoroastrians (304,000) to Zimbabwean animists (3.52 million)? Though Barrett says he publishes factual, unbiased data, he readily acknowledges it has a purpose: to serve as an informational undergirding for Christian missionary work.
"I don't have the gift of evangelism through personality. I don't have the gift of traditional preaching," explains the soft-spoken Barrett.
Is he a missionary, then? "Certainly, but not the shouter on the street."
He calls his blend of religion and science "missiometrics."
Barrett's encyclopedia shows immense global shifts between 1900 and 2000 in various faiths' shares of the global population. Though Christianity became the first truly universal religion in terms of geography and remained the biggest, it lost a bit of market share. Second-ranking Islam expanded considerably and Hinduism somewhat, while Buddhism declined. Chinese and other folk faiths dropped precipitously, as did Judaism.
The non-religious or atheistic category, negligible in 1900, claimed nearly a fifth of the world's people at one point but has declined since European Communism's fall.
Today, Barrett and his tiny staff work in a Presbyterian church basement in Richmond. They're producing a CD-ROM version of the findings, as well as analytical articles. It's a long way from his beginnings.
A one-time nonbeliever, Barrett made a born-again Christian commitment as a Cambridge University undergraduate.
A year later, he says, "I woke up in the middle of the night and became convinced that Christ was present. I can't explain it. I heard Christ say, 'You ought to go to the ends of the world.' "
His ordination after years in science let him respond to this dramatic missionary call.
Barrett was assigned to Kenya to conduct a field survey of Africans' complex church affiliations. That research was the start of his lifelong specialization, and of the global counts in the first edition of his encyclopedia.
But Barrett had to cope with turmoil in Nairobi, his longtime operations base. His research office was hit by machine-gun fire and then thieves ransacked the place, making off with books, computers and floppy disks full of data. Fortunately, the first edition was already in print, so the losses were limited.
In 1985, 28 years after he arrived in Africa and three years after his encyclopedia first came out, he reluctantly sought refuge in the more placid Richmond, Va. There, he had been offered an office and logistical support at the Southern Baptist Convention's foreign mission board.
But Barrett prizes independence so he later shifted to an independent research agency, Global Evangelization Movement. Still an Anglican missionary, Barrett continued to get approval for his work from the Church Missionary Society in London. A young U.S. Presbyterian layman, Todd M. Johnson, signed on in 1989 as co-editor.
The biggest Christian shift since the encyclopedia's first edition is the emergence of the 386 million "independents" as the second biggest category, after the 1 billion Roman Catholics.
These independents worship in indigenous churches, mostly in developing countries. Sizable examples: Brazil's Universal Church of the Kingdom of God, the Jesus is Lord Fellowship in the Philippines and South Africa's Zion Christian Church.
Barrett thinks their growth could prove as important as the 16th-century rise of the Protestants, who now rank third with 342 million. Orthodox number 215 million; Anglicans, 80 million.
The independent churches have no formal ties to those three Christian categories or Catholicism. The independents are forming networks somewhat like traditional denominations but style themselves as "post-denominational," Barrett says.
Barrett watched the independent sector's growth up close. When the Anglicans first posted him to Kenya in 1957, he was supposed to work alongside an African priest, Matthew Ajuoga. But Ajuoga had just joined a big breakaway of African independents and Barrett was forbidden by the Anglican hierarchy to contact him.
Today, Ajuoga heads an alliance of 85 million African independent church members.
Another global trend that Barrett's encyclopedia describes is the rise of Pentecostals, who believe in receipt of "gifts" of the Holy Spirit, including speaking in tongues. He also notes increases in the similar Charismatics in traditional denominations, and "Neo-Charismatics" in independent churches.
Barrett and Johnson call themselves Charismatic, part of the Holy Spirit movement in old-line denominations, and their estimate that the related Pentecostal and Charismatic movements encompass 524 million believers will be one of their work's more controversial statistics. No one else has attempted such an estimate.
The encyclopedia is interested in material as well as spiritual needs. It calculates that only 44 percent of the world's people are living comfortably, with 10 percent "scraping by," 28 percent "poor and needy" and 18 percent "destitute."
As the encyclopedia documents, Christianity's population center is inexorably shifting. Growth is in the Southern Hemisphere especially, notably in Africa.
Johnson, who may succeed Barrett as the world's top soul-counter one day, sees that Christianity started out the past century 81 percent white and ended at 45 percent. And he knows that's not going to stop.
"This is a huge change, not just ethnically but in what Christianity is all about. Christianity is steadily moving from this Caucasian, European-dominated, modern way of life, even beyond Christianity as an institution," he says. "There's no central, unifying narrative."