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The Rate of Christian Growth

I have been discussing the fascinating article by Keith Hopkins, “Christian Number and Its Implications,” about how many people converted to Christianity at certain points of time (say, from ten years after Jesus’ death to the time the emperor Constantine converted in the year 312).  As we have seen so far, the first problem Hopkins deals with is how to count – that is, who counts as a Christian?  Hopkins takes the (in my opinion) justifiable and sensible view that if someone considered themselves to be a follower of Jesus (whether they were proto-orthodox, or Sethian, or Marcionite, or Ebionite, or anything else) they should be counted.

The second problem, as we have also seen, is that our sources don’t give us any reliable statistics, or indeed statistics of any kind.  Instead, our sources (and, by the way, without sources we have no evidence, only guess work, even if it is educated guess work) are highly prone to exaggeration.  And so the book of Acts indicates that within a couple of months, some 8000 Jews in Jerusalem had converted.  As I’ve pointed out already, that can’t be right.

And so what do we do?  At this point Hopkins refers to the interesting study of Rodney Stark, in his book The Rise of Christianity.   Let me stress that Stark is not trained as a historian of early Christianity.  He is a sociologist who studies modern religious movements, such as Mormonism.   But as a sociologist he is very good at crunching numbers.  And in his book he crunches the numbers, coming up with some very intriguing and somewhat mind-boggling results.

Let me say before going any farther that Stark’s book was highly controversial.  He tried to establish how quickly Christianity grew.  That was the most compelling part, as I’ll be pointing out in a moment.  But most of his book was about why Christianity grew, and here he came up with some ideas and theories that simply have not seemed overly persuasive to most historians in the period, in no small measure because he did not have a very sophisticated approach to the surviving sources of the period, unlike his sophisticated approach to number-crunching.

So let me talk about the number crunching, since this also is the issue that Hopkins too wants to focus on.   Stark points out that most historians who have tried to explain the growth of Christianity have taken rather wild guesses about how to make sense of it.

Here are the data: Christianity started out as a small group of Jesus’ followers after his death – his disciples and a handful of women who came to believe he had been raised.  That much seems pretty certain and is what is reported in the New Testament itself.  There seems no reason to question or deny it.   Moreover, there is widespread agreement that even though we can’t know the exact numbers, or anywhere near the exact numbers, it appears that by the time the emperor Constantine converted, maybe 10% of the empire (or 5% or 15% — let’s just say 10%) was Christian.  It is almost always thought that the empire comprised 60 million people (give or take 10 million) at the time.   So while admitting that we’re talking ballpark numbers here, let’s assume that there were, say, 6,000,000 Christians at the beginning of the fourth century.

So the question is, how do we go from a handful of Christians at the beginning of the period we are interested in to 6,000,000 at the end?

Most scholars have preferred one of two options.  Either the growth was completely miraculous and requires the intervention of God or (or rather and/or) there had to be massive conversions of the sort you would get at a Billy Graham crusade, where at any one moment a Christian evangelist managed to convert hundreds of people to the faith at one time.  That just makes sense to most people who try to figure it out.  There must have been massive conversions to explain it, right?

Wrong.   Stark is a number cruncher.  And he studies modern religious movements, where you can actually count the converts (roughly).  And he points out that in fact it is not a matter of speculating about massive conversions.  It is about math.

For his math problem, Stark points out that the book of Acts has thousands of people converting right away in the first few months.  OK, that’s probably an exaggeration.  So let’s just say that by the year 40 CE – ten years after Jesus’ death – there were 1000 people who considered themselves Christian.   And let’s say that by the year 300 (again, we’re just doing guestimates and round numbers here for the sake of illustration) there were indeed 6,000,000.   How do we get from 1000 to 6,000,000?

All we have to do is set up an equation and figure it out.  We can safely assume that the rate of growth won’t be steady and invariable.  The rate will fluctuate over time.  We’ll admit that.  But we’ll also acknowledge that the more Christians there are, the more other people they’ll be able to convert.   If five Christians are able to convert five other others, then five hundred Christians will surely be able to convert a lot more than just five others – say, they’d convert roughly the same number, they’d convert 500, in *roughly* the same amount of time.  So if there is *roughly* the same approximate rate of conversion over time  the more Christians there are, the more converts they would be making.

And so you simply need to figure out what kind of rate of growth is needed (it will go up and down, but you only need an average).  Stark crunches the numbers.  If you start with 1000 Christians in the year 40 and end up with 6,000,000 Christians in the year 300, you need a rate of growth of (only) (about) 40% a decade.   That is to say, the 1000 in the year need to grow only by 40 by the year 50, so that then there are 1400 Christians.  By the year 60, with the addition of another 40% more; by the year 70 another 40% — keep doing the math: by the year 100 there need to be only 7400 Christians; by year 200 then there will be 210,000; and by the year 300 there will be 6,000,000.

It’s not a matter of miracle necessarily.  And you don’t need massive conversions at any point.   Assuming a steady rate of grown, where every ten years each ten Christians manage to convert, between them, only four more people to the faith, then you get to 6,000,000.   Stark is a bit more precise.  He concludes that you need a rate of grown of 43% per decade.

And for him, as a sociologist of modern religion, this is not at all implausible.  On the contrary, it’s both believable and highly interesting.   As it turns out, it is the rate of growth of the Mormon church from the time of its founding until today.

It is not a matter of miracles; it’s a matter of steady growth, and it can be accounted for by an exponential curve over time.

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How Many Christians Were There?
Paul in a Nutshell and NT Views of Crucifixion: Readers Mailbag May 13, 2016

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Comments

  1. RonaldTaska  May 15, 2016

    I had been wondering what you thought of Stark’s book. Thanks for starting your review of it.

    So, 40% growth a decade is all it takes and this is the growth of Mormonism. How interesting. It’s sort of like compounding interest.

  2. Benjamin
    Benjamin  May 15, 2016

    does it matter how they grow? Winners write and rewrite history. Obviously in the future when something else over taken this religion, they can do an honest job to describe the growth of these Christians.

  3. Wilusa  May 15, 2016

    But…how can one assume all converts will succeed in converting others? Or will even try to convert others?

    Some people are reticent, just don’t have the personalities that would induce them to coax others to adopt their views.

    And there might, in a given region (let’s say a city), have been only a certain number of people who, for one reason or another, would have found this new faith appealing. Others would have rejected it, and never given it another thought.

    By the way, should the “count” of Christians include members of the actual converts’ families, who were probably never given a choice?

    • Bart
      Bart  May 16, 2016

      Yes, that’s the point of rate of growth: not everyone *needs* to convert others. Only a few need to convert a person now and then.. The “count” would include anyone who considered themselves Christian for whatever reason.

      • Eric  May 19, 2016

        Right. In any group of ten Christians, for example, if there were, on average, only one “evangelizer”, he wouldn’t have to be very effective to meet this rate. He’d need to convert 4 people over ten years, or only one every 30 months.

  4. talmoore
    talmoore  May 15, 2016

    Dr. Ehrman, another important point is to distinguish between the conversion of adults and the raising of children from birth as confessing Christians. Once Christianity became a part of childrearing in general (as it was with Judaism), we’re talking about some serious growth. My educated guess would be that Christian parents really began unculcating Christian beliefs into their kids starting in the 2nd century, but we see that even as late as the 4th and 5th centuries men such as Augustine came to Christianity rather late in life, even with a Christian mother.

  5. Omar6741  May 15, 2016

    Professor Ehrman,
    Is it true that the Romans were still trying to force pagan communities to convert to Christianity all the way into the reign of Justinian? That is an amazing bit of information, if true: after all that effort, and after about two centuries of being an official religion of the Empire, there was still a need for forced conversion!

  6. Rick
    Rick  May 15, 2016

    I get a simple average annual growth rate of 3.4%…..
    Urban Legend has it that Einstein said the most powerful force in the universe is compound interest….

    260 years is a long time at 3.4%

  7. godspell  May 15, 2016

    Of course, only 2% of Americans are Mormons, seems unlikely it’s getting much higher, and they’ve made few inroads outside the U.S., in spite of Mitt Romney’s valiant efforts in France. And Mormons didn’t have to convince anyone Jesus was God–they just tweaked something that already existed, piggybacked off an already well-established evangelical Christian culture (got their book in hotel rooms next to the Gideon Bible).

    Their main handicap to conversion (that also led to sometimes violent repression) was polygamy, but of course before that was jettisoned for pragmatic reasons, that also allowed for rapid growth without necessarily being successful evangelists–just have more kids and raise them Mormon! Early Christians didn’t have that. I see young Mormons in their suspenders and white shirts out drumming for converts in my North Manhattan neighborhood. They aren’t finding many takers. Inspired a hit Broadway Show, which is something. They need to do something about that dress code. The Jehovah’s Witnesses are so much snazzier (and a lot less blindingly white).

    To say something CAN happen isn’t showing how it DID happen. Let’s be crass, and say a new religion is a product looking for a consumer base. You don’t only need to explain how the product was sold–you need to explain why there was such a ready market for it. What was missing from the lives of some pagan Romans that Christianity filled? Because there were many other new religions out there trolling for converts. If people had been happy with the religion they had, they wouldn’t have abandoned it so readily, to embrace a faith that meant potentially being accused of sedition (for not sacrificing to the Roman gods). What did Christianity have to offer that the other religions did not? It can’t just be exclusivity and evangelism–like a spiritual Pyramid Scheme. There had to be positive benefits that came with membership.

  8. DeanMorrison  May 15, 2016

    “That is to say, the 1000 in the year need to grow only by 40 by the year 50, so that then there are 1400 Christians.”

    I think you meant to type 400, not 40 😉

  9. Greg Matthews
    Greg Matthews  May 15, 2016

    Can you recommend any book(s) on migration and social movement in the Roman world at the time of Jesus, particularly in the Levant? I see where Brill has a new one out, but I think it’s strictly on Rome, but even if that weren’t the case it’s way outside my price range. In particular, everything I keep reading tells how highly mobile people were at the time, moreso than at any other time in history until the 1800s! With that in mind I just keep having questions about how the early Gospels, Q, L(?) and M(?) were so slow to get from Christian group to Christian group. Seems like Paul’s letters spread relatively rapidly.

    • Bart
      Bart  May 16, 2016

      You might check out the articles by Eldon Epp on the migration of manuscripts based on what we know from the findings at Oxyrhynchus (in his collection of essays on Perspectives on NT Textual Criticism.

      • Greg Matthews
        Greg Matthews  May 16, 2016

        Great, thanks. I’ve read his book on Junia and he’s easy for me to follow, unlike some scholars who have trouble stringing together words 🙂 Looks like those came from Novum Testamentum. I wish that journal was more affordable, I’ve bought a few of their individual articles 🙁

  10. shakespeare66  May 15, 2016

    I am wondering if that rate of growth gets us to where we are today?

  11. Pattycake1974
    Pattycake1974  May 16, 2016

    I’m sorry to be so oppositional, but Stark isn’t convincing me either. Mormons didn’t undergo persecution the way early Christians did. That’s like comparing apples to oranges. Did he write anything about children being brought up in Christian households who would have likely grown up, married other Christians, and had their own children who naturally became Christians? How many people died under Nero or other types of persecution? How many people died in the Age of the Martyrs before Constantine put a stop to it? Did Stark factor any of these things into his calculations?

    Paul (and how many others–not sure) were establishing churches all over the place and there’s only 1400 Christians by the year 50 and approx. 1,960 by the year 60. That’s about 50 people a year. That sounds extremely low.

    What I keep seeing (maybe erroneously) is that Christianity was spreading rapidly, but it met with so much opposition that it was partially underground.

    • Bart
      Bart  May 16, 2016

      The opposition to Christianity is overplayed in the popular imagination. You might like reading Candida Moss, The Myth of Christian Persecution.

      • Pattycake1974
        Pattycake1974  May 16, 2016

        Okay, I’ll add it to my list.

        So, when reading scriptures with numerical values placed to them, are they supposed to be read in a literal sense? Jesus fed the 5,000…did they truly mean 5,000 or as a figure of speech?

        How can we read Acts in a literal way, when Luke knew that those numbers were impossible?

        • Bart
          Bart  May 17, 2016

          I don’t think the numbers can be literally true (if the stories happened at all!). Luke almost certainly thought the numbers were possible, but even he knew that he didn’t know the exact numbers.

      • godspell  May 16, 2016

        A myth as presented in popular culture, but there were periods of severe persecution for early Christians, and indeed it’s in that context we get most of the early instances of literate Romans mentioning them. Don’t want to run from one extreme to the other. It was a risky business, saying the gods of the Roman state did not exist and therefore you would not sacrifice to them, or to the Emperors who had been declared gods after their deaths. Nobody cared what you thought privately, but Christians wanted to profess their faith openly, practice it exclusively, which is where the problem lay. It’s a myth that Christians were perseucted most of the time, but there was never any way of knowing when the persecution would return.

        And of course Mormons were persecuted. Joseph Smith was lynched. The community he founded in Illinois (Nauvoo) was under siege from neighboring Christians who (apparently without a sense of irony) persecuted Mormons for being polygamists, and for having their own scripture that purported to be the completion of Christian scripture.

        And when I say persecuted, I mean attacked by large parties of men armed with guns, which I certainly think qualifies as persecution. Dislike and distrust of them was so widespread for decades afterwards that A. Conan Doyle made villainous (and lecherous) Mormons in Utah part of the backstory to A Study in Scarlet, the first Sherlock Holmes mystery. He’d probably never even met any Mormons at the time.

        Difference is, the Mormons fought back, often gave as good (or bad) as they got. The early Christians mainly didn’t. If they had, they might well have been exterminated, but passive resistance, within certain limits, can be an effective response to persecution. The Mormons had to mainly absent themselves from settled areas of the U.S., go west, ghettoize themselves for a time (and have a whole lot of children, which I really do think you have to factor in–polygamy was a major element in their early population growth, and many still have very large families) The Christians just stayed where they were, mainly blended in, and were (to all accounts) mainly very good neighbors. Still waiting for the Kingdom to come in the early days, so they had to be on their best behavior.

        Obviously Jews weren’t under persecution at all times in Europe, or African Americans at all times in America prior to the Civil Rights movement, but nobody would argue they were not persecuted for being different. I wouldn’t deny the heavily mythologized elements in stories Christians later told about that persecution, but as with Jesus himself, that doesn’t mean they were making it up out of whole cloth.

  12. Kazibwe Edris  May 16, 2016

    Dr Ehrman

    i don’t understand why matthew would use “the church” in
    5If your brother sins against you, go and confront him privately. If he listens to you, you have won your brother over. 16But if he will not listen, take one or two others along, so that ‘every matter may be established by the testimony of two or three witnesses.’ 17If he refuses to listen to them, tell it to the church.

    would the words in greek “the church” have been known in palestine in jesus’ day?
    anybody else uses these words to describe religious gatherings or assemblies in /before jesus’ time?

    • Bart
      Bart  May 17, 2016

      No, probably not. That’s why it is usually thought that this is something jesus did not actually say.

  13. bmacrae  May 17, 2016

    My 2c worth. As with almost all statistical analysis, I think we need to be a little careful with the headline numbers. To grow at 40% per decade, the Christians needed to recruit sufficiently to replace those who had died + grow. If life expectancy was 50yo, then around 20% of the population die in a decade (I think). Using the 1000 Christian example and assuming 200 die in that decade, they need to recruit 600 additional Christians. Notwithstanding, the principle is still the same, just the numbers slightly bigger. Did Stark cover replacing those Christians that died?

  14. ugalaw97  May 18, 2016

    Starke infamously predicted in the early 80s that the LDS church would grow to over 280 million by 2080 and he used it as evidence validating his highly influential (well for a while anyway) methodological innovation that made him famous in sociology of religion- using economic theory to construct a rational choice model to predict changes in religious demographics where religion was considered a consumer good with churches competing for customers in a perfectly free market. It was also his attempt to reorient the field away from secularization paradigm which was being challenged as applied to the US which was not following the rest of the developed world which matched classical secularization theory. There has always been tension in the field of SofR between the liberal protestant scholars who dominated the field until a new generation of more secular academics replaced many of the protestants in the 50s and were eager to improve its reputation as a legitimate science in the wider academy. Starke was unique in that at the time he was not religious, embraced a quantitative scientific ethos but was invested in disproving secularization by demonstrating that the US was an anomaly where religion flourished. As he published throughout the 80s and 90s he grew increasingly more conservative, converted to evangelical flavor of the christianity and took charge of Baylors religion department and research center which makes little attempt to hide it’s faith promoting mission. Much of his work has subsequently been disproven, including his mormon growth predictions. Ryan Cragun is a sociologist who has challenged much of Starkes work on the LDS church. Here is an article from a few years ago summarizing the problems with his mormon growth rate http://religiondispatches.org/mormon-numbers-not-adding-up/ The problems with his work seem to be more to do with relying on the churches own reports rather than his methodology but you may want to check recent published work to be sure. I’m not sure if his free market modeling was baked into his historical calulations because sociologists are highly skeptical of those assumptions that are still taken as axiomatic in economics.

    • Bart
      Bart  May 19, 2016

      Interesting. Thanks. Yes, his more recent book on the Triumph of Christianity strikes me as much more conservative than his earlier work.

  15. llamensdor  May 20, 2016

    It seems to me that we should consider what is meant by “conversion.” You did not have to be a member of a priestly family or a graduate of the Jerusalem Theological Seminary to qualify. Paul’s genius consisted primarily of 2 principles: (1) it was easy to become a Christian. All you had to do was acknowledge Jesus as your savior; perhaps get doused with some water. Jesus was a “real” person as compared to the Hebrew God who was invisible and harder (if not impossible) to visualize. And you didn’t have all those messy Jewish rules – circumcision, kosher foods, etc. It was even easier than being a dues-paying pagan; (2) As lousy as life was for you in the present, you would be rewarded in the hereafter—and Paul’s major stroke—the hereafter was coming any day now, and you better sign up before it’s too late. Paul and his successors had to fudge about the apocalypse, but we still have sects who are claiming October 27, 2017 is the judgement day. It’s still a helpful concept for evangelists. Did Paul personally believe in the product he was peddling? That’s a question for another day.

  16. Greg Matthews
    Greg Matthews  May 29, 2016

    Do you know if there’s an online source for this article you’ve referenced? I can only find the abstract at the Project MUSE website and it looks like neither they nor the Journal of Early Christian Studies sell individual articles. There are different formulas that can be used for population growth and something about these numbers isn’t adding up the way they should. I’d like to see how Hopkins explains this.

    • Bart
      Bart  May 30, 2016

      I”m afraid I don’t know. I was able to get it through my library…

  17. fabiogaucho  July 5, 2016

    Bart, do you think reproduction rate could have been a factor? If Christians practiced infanticide and abortion at much lower rates, their percentage would presumably grow generation after generation.

    • Bart
      Bart  July 6, 2016

      That’s the argument that Rodney Stark makes in The Rise of Christianity.

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