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Growth Rate of Early Christianity

Time to answer a readers’ question, as a change of pace, unrelated to anything else I’ve been posting on:


The question on my mind is almost certainly NOT knowable, but I will ask it anyway.

1 – can anyone estimate how many Christians (all variations included) were abroad on Planet Earth at any given time in the 100s or 200s?

2 – when Constantine chose to back Christianity and make it the “official” religion — in the early piece of the 300s — how many actual Christians were there? Or, to make it easier: Taking the whole “Roman” empire as 100%, what pct of the peeps were Christians?

3 – A few generations later (380?) — Theodosius I said that the Roman Empire officially believed what the Bishop of Rome believed. How many (or what percentage of the people) were Christians in 379?

I don’t expect precise answers. Any pointers you could provide to where answers might be found (or guesstimates, even) by researchers/experts/theologians/atheists or even hockey players would be appreciated.


This is an excellent question (or set of questions).  It’s not clear if scholars actually know the answers, but they have offered some!    I will give the short answers.  If you are interested in pursuing the matter further, I’d suggest two VERY different books (i.e. different from each other): Ramsey MacMullen, Christianizing the Roman Empire (MacMullen is a social historian of ancient Rome, a real expert in antiquity); and Rodney Stark, The Rise of Christianity (a highly controversial book that was not well received by scholars; Stark is a sociologist of modern religion who tries to apply his craft to the ancient world.  He actually doesn’t know enough about the ancient world to make it work, but as a sociologist he knows how to crunch numbers, and that’s where he’s really interesting).

So, the basic story is this.   There were probably about 60 million inhabitants in the Roman Empire, give or take, throughout the first four centuries CE (the period you’re asking about).  It is almost universally thought that Christianity started out as a  very small movement – say about 20 people a few weeks after Jesus’ death.

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  1. Adam0685  April 23, 2013

    The guess of about there being only 20 people following Jesus after a few weeks following Jesus’ death seems a bit low. If that’s the case, given that Jesus is said to have preached to “the crowds” in the gospel (however defined – whether as “a large number of people” or the generic “public”) for maybe three years and out of all the people (hundreds? dozens?) that may have heard his message only 20 “followed” (however defined – believe his message? left everything they had to literally follow him around?) suggests that his message was not that appealing enough to people who heard his message during his lifetime. I guess we can see hints of a lack of response to those who heard his message in the gospels (perhaps Mark 4:10-13, Matthew 7:13, etc. suggest this).

    Given that so few may have followed him during his three or so year ministry I wonder if after Jesus died people who began to covert converted because of what he said (if they didn’t follow him during his lifetime, why after?) or because of how his followers interpreted and reinterpreted his words and the fascinating claim of the resurrection.

    • Bart Ehrman
      Bart Ehrman  April 24, 2013

      My “20 people” is meant to refer to the people who came to believe that he had been raised from the dead in the couple of weeks or so after his crucifixion. I’d be surprised if there were many more than that…

  2. RonaldTaska  April 24, 2013

    Nice and different post with good questions and good answers. It is sort of like investing in a 401k 40 years ago and having it slowly grow each decade until after four decades it has grown considerably.

  3. tawfiq  April 24, 2013

    What would also be interesting to know is how the numbers and distribution of Christian-Jews varied during the first 400 years of the Common Era. I have often wondered if the references to ‘the poor’ in the Gospels were in some way a coded reference to the Ebionites.

    • Bart Ehrman
      Bart Ehrman  April 24, 2013

      Yes, there are different opinions on that. My own view is that Jewish converts became few and far between after the first 20 or 30 years. In any event, the “Ebionites” were a later group who did claim to represent the views of the earliest followers of Jesus, but they cannot be attested till the second century.

  4. gmatthews
    gmatthews  April 24, 2013

    Great question and thanks for answering it! Assuming Jesus really did have around 12 main apostles and that they were as reasonably close to him as the bible suggests, and that they (“they” being others like Andrew, Bartholomew, etc— assuming they existed!) were as likely to proselytize as others more well known like Peter, James and Paul then the churches that were established (such as those known from Paul’s letters) must have had tiny congregations in the first few decades! I’ve never really thought about it before tonight, but I think in my mind I probably pictured the church’s that Paul wrote to as having maybe 20-30 people in them, but if your numbers for the first few decades are correct then they must have been much smaller than that, perhaps just a dozen or so per church!

    Does that sound right?

    • Bart Ehrman
      Bart Ehrman  April 24, 2013

      I wish I knew! I’ve thought about it a lot. We know that church in Rome had several dozens — see Paul’s greetings in Rom. 16. But I don’t know what his average church had. 15 people? 25? 55? I wish I knew!

  5. Jerry  April 24, 2013

    I read Stark’s book. Stark’s starting numer was 1000 Christians in 40 AD with a 40% growth rate per decade. At that rate, in 350 AD, there were 33,882,005 Christians in a population of 60 Million, or 56.% of the Roman Population.


    • Bart Ehrman
      Bart Ehrman  April 24, 2013

      Ah, right! My guess is that 1000 is a bit optomistic for 40 CE, but that 33 million by 350 is also optomistic. So it may even out in the end. MacMullen’s numbers are more compelling, I think (about 30 million by the end of the fourth century, I think)

  6. Dennis  April 24, 2013

    Science forbid!

  7. samchahal  April 24, 2013

    fantastic post this, I have read up on this info before but good to be reminded afresh! thanks Bart, now I can explain with confidence that it certainly wasnt divine intervention of any sort!

  8. Wilusa  April 24, 2013

    As a person of Irish and English descent, I’ve long thought that my earliest ancestors who “converted” to Christianity were forced to practice it, and to pretend to believe the doctrines. (“Forced,” at least, by social and economic pressure.) I’ve imagined that it was only after three or four generations of indoctrination by the clergy that ancestors of mine came to really believe in Christianity, and think their forefathers had experienced genuine conversions.

    I’ve assumed the ancestors of most Jews and Muslims came to those faiths in much the same way. Do you agree?

    About that growth rate for early Christianity…I find it hard to understand how the growth rate could have equaled that of the Mormons, when modern means of communication (and travel) have made it so much easier for the Mormons to reach out to potential converts.

    • Bart Ehrman
      Bart Ehrman  April 24, 2013

      I’m not sure that forced conversions happened at all in Judaism, and I doubt if they happened much in Islam. As to Mormons, I believe most of the conversions happen not because of radio and TV, but because of personal contacts with Mormon neighbors, friends, family, etc. — all of which was how it worked in antiquity for the Xns as well….

    • Jonathan_So
      Jonathan_So  April 27, 2013

      On Jews and Muslims and forced conversion, if I recall correctly, that wasn’t a very big thing until the Crusades. The Fustat Geniza documents show that Jews and Muslims did have trade partnerships without necessarily having to convert, at least in the 800s-900s. forced conversion for Islam is pretty spotty other than under the Safavid, where the Jews basically had to pretend to convert (sort of like how early christian lapsi) you got like about one or two caliphs taking it as a policy and thats from about the beginning to the Ottoman empire. then you have Sabbatai Zevi in 1668 who was basically given the option to convert or die.

    • philologue  April 27, 2013

      Yes, but forced conversions can’t happen in the very beginning phases of a religion, when its adherents are a (often persecuted) minority. That requires a social majority that can wield a certain amount of power. Christianity, Mormonism, and Islam all experienced a certain amount of feigned conversions, but only once they became the social ‘norm’, and there was some kind of social advantage to be gained by appearing to follow them (and despite the fact that Christian and Islamic doctrine firmly forbid ‘forcing’ one’s beliefs on someone). Judaism on the other hand, is as much a nationality or ethnicity, as a set of beliefs (you’re either a descendant of Abraham/Isaac/Jacob, or you’re not), so to my knowledge it’s never been either in a position of strength to force conversions, or even been interested in doing so. All that’s just my own thoughts, and open to correction.

  9. RecoveringCalvinist  April 24, 2013

    I remember you wrote about the existance of an ancient letter accusing Christian converts of being a poor and uneducated lot, attractive to a disproportionate number of slaves, women and children. Next question, what sort of people were attracted to the early church?

    • Bart Ehrman
      Bart Ehrman  April 24, 2013

      In the earliest stages it appears to have been a lot of the lower classes. Of course, there were a lot more of them to start with!

  10. gavm  April 24, 2013

    we can prob assume islam has had some pretty impressive growth rates in its time too. i suppose there are people who think thats a miracle as well.
    it must be remembered religion works by a type of “natural selection”. only the religions that had the features which allowed them to convert followers and put the brakes on other faiths are the ones that have been successful over the years and hence we are familiar with today. we shouldn’t be surprised that christainity, islam ect have had large numbers of followers in the past or we wouldn’t know of them today.

  11. hwl  April 24, 2013

    …only if we first get a Mormon President.

  12. JamesFouassier  April 24, 2013

    In a similar vein, I’d love to know more about how Christianity spread in its first 20 years or so. Do we know anything with any degree of certainty, or even factual support, or is it all speculation ? Paul didn’t establish all the churches with which he corresponded; he found some already there. Twenty or thirty years after Jesus’ death Paul finds churches already established by others ? So far from Jerusalem ? By whom ? How ?

    • Bart Ehrman
      Bart Ehrman  April 24, 2013

      the only church that Paul writes to that he didn’t found was the one in Rome. all the others were his. But almost certainly there were churches established by other missionareies as well, who may have felt, like Paul, called to spread the message.

  13. ptalbot  April 24, 2013

    Thank you for a really interesting article. I read Rodney Stark’s book a few years back and (as an interested non-expert) I found it fascinating and convincing, particularly his arguments (and this is from memory) that Christianity may have been so attractive to pagans for social reasons such as greater freedom for women and Christians’ willingness to nurse their sick pagan neighbours back to health during infectious epidemics when other pagans would have left them to die in their haste to leave the affected area. I didn’t know it had been so poorly received by scholars. Could you briefly expand on their reasons for criticism or point me towards a constructively critical review?

    • Bart Ehrman
      Bart Ehrman  April 24, 2013

      I may take this on at some point, as I’m planning eventually to write a book about it. One serious question is whether there is any *evidence* that the factors you mention led anyone to convert….

      • dennis  April 25, 2013

        I read an article ( sorry I’ve forgotten author ) some while back that theorized the growth of Christianity in the urban Empire was due primarily to its ” open door policy ” of admission ( no gender class and especially no ethnic barriers ) . If you are newly arrived in one of the great cities from a tiny village where you had known everyone else since birth , total immersion in hundreds of thousands of strangers who don’t look , speak or act as you have always expected others to do must have been extremely stressful . If you were invited to join a group of people who honestly seemed to care about you and provided a network of people you can trust , the attraction would probably be very strong indeed . Many ( most ? ) of the members would join and stay far more for social reasons than for any Theological concern . Perhaps a similar process could be at work in today”s mega-churches ?

        • Bart Ehrman
          Bart Ehrman  April 27, 2013

          Yes, it’s an interesting view. I think the problem with it is that there aren’t any ancient sources that suggest these to have been factors. But who knows?!

  14. Richard Jacobsen  April 24, 2013

    The severe Shortage of Lions between for the first 500 years after Jesus’ Crucifixion.

    • Bart Ehrman
      Bart Ehrman  April 24, 2013

      Sorry — you’ve lost me!

      • tcc  April 25, 2013

        It’s a “Christians got fed to lions” joke–the reason Christianity took off is because there was a shortage of lions around that time.

        I’ve been getting pretty interested in Julian The Apostate lately. How much of a threat was that guy to the third century church, and do you think he would have succeeded in bringing Paganism back to the forefront if he hadn’t died in battle?

        His book “Against The Galileans” makes some observations that actually turned out to be right; Genesis isn’t describing a creation from nothing, it’s describing Yahweh making the World using pre-existing material (separating the waters from the waters), and Yahweh was originally just a tribal god in Edom that moved up a pantheon due to geographical and political reasons, etc.

        • Bart Ehrman
          Bart Ehrman  April 26, 2013

          It’s a great quesiton — and one for which we have no answer! Things certainly would have been different if he had reigned for 40 years! Maybe it would have changed everything.

      • gavm  April 25, 2013

        i think hes making a joke about not enough lions to eat christains hence they grew in number rather than being digested

    • Jim  April 25, 2013

      Richard, are you suggesting a parabolic curve – if a lion feeds on too many martyrs it gains weight and becomes too slow to chase subsequent potential dinners?

    • Richard Jacobsen  May 11, 2013

      Sorry, didn’t mean to lose anyone. I believe the numbers to be inflated given the fact that there were many religions present in Rome at the time of Constantine and the following Caesars were not Christian. There were so many Pagan, Mithra followers, and just plain Hedonists it would be hard to believe the conversion rate would be so fast and so extreme. Could be totally wrong believing this given the outcome, assertions, and atrocities the Catholic Church got away with in the course of its history; but lying would have been one of their good characteristics. .

      My comment about lions was black humor. If the Romans were feeding Christians to the Lions perhaps a few more would have saved us from the horrors the church practiced over the last 2000 years.

      Many watched a debate in London in 2009 Between Christopher Hitchens, Steven Fry, Cardinal Onaiyenkan and Ann Widdecombe on whether the Catholic Church was a Force for good in the world. While Mr. Hitchens and Fry are clearly seasoned debaters and Hitchens an intellectual of courage to speak his mind, they clearly not only one the debate against the Church being a force for good and changed peoples minds, but made the other side look like fools.

      It is fascinating whether you agree with Mr Hitchens or not or just believe him to be the town bully. But he can and does point out how ridiculous religions are. Whether it is holding on to the belief that a condom is the bogey man of reproductive rights or that modern science is again something that we should be afraid of.

      So the accelerated growth of Christianity is something that not only should we question, but if it is correct it is something to be afraid of. Why afraid? What if the next bigger better machine comes to town. Will the people that jumped on the Christian band wagon so quickly move fast to the new shiny toy. They were fast to join the last one. It is only a small step from disagreeing with someone to burning them on the on the post and we haven’t come that far. You need only look at the last election and listen to the rhetoric. We really have people today that think that Leviticus, Genesis, and Coke are the real thing, everything else is as lie made up by that crafty devil.

      David Barton has everyone thinking Jefferson, and Adams wrote the Constitution just for White people right out of the Bible. Many have even heard that guy say the Founding Fathers believed in Creationism over Evolution which is a neat trick considering Darwin wasn’t born for almost 100 years after the the Constitution was written.

      So it is a shame we didn’t have more lions near Rome that were hungry.

  15. screwtaperocks  April 28, 2013

    I have two very pithy comments.

    I believe that current polling data has shown that the fastest growing religious group is actually the “Non-religious/Unaffiliated” which is no doubt made up of a whole host of folks that believe in something supernatural, but is also comprised of agnostics/atheists.

    Secondly, I have my doubts about the Mormon church growth rate (especially if it is dependent on self report data).
    It is quite easy to grow your numbers quickly if you can baptize dead folks into the faith.

    And, Bart, I don’t think it will take 200 years for all of us to become Mormons. They probably have -your- proxy picked out….. right now. I bet when you wrote that last line of this blog post you never could have imagined you were speaking quite literally. 😀

  16. Richard Jacobsen  May 11, 2013

    Sorry won not one

  17. tccullen  July 1, 2014

    Hi Bart,

    I am in the process of reading Rodney Stark’s book. On page 78 he states “it is taken for granted that Jesus and his disciples spoke Greek in their daily life”. This seems to conflict with the picture of the disciples as poor, illiterate, Aramaic speaking fisherman/farmers I recall from reading some of your earlier books? Makes me not want to continue reading Rodney’s book.

    Thanks for your time.
    Tom Cullen

    • Bart Ehrman
      Bart Ehrman  July 2, 2014

      Yes, that’s a big problem! But Stark isn’t a historian — he’s a sociologist with an interest in history.

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