We often think of communities as organic creatures, which come into existence and grow on their own. However, the truth is they are fragile blossoms. Although many communities surely germinate and bloom on their own, purposefully creating communities can take a tremendous amount of hard work, and one factor their success ultimately depends upon is their numbers.
If a community is too small you'll often have insufficient critical mass to sustain it. Conversely, if it's too large you can end up with a community that's too noisy, too cliquey, or otherwise problematic. These optimal and sub-optimal community sizes appear in strata, like discrete layers of rock. For a community to advance from one strata to the next often takes immense energy.
We can analyze these community sizes in three ways. In this first article I'm going to talk about numerical group thresholds that have been observed in various sizes of tightly-knit communities, while in its sequel I'm going to talk about personal thresholds and how they relate to group thresholds. In my final post, I'm going to consider how power laws and inequalities of participation further complicate these simple values in the creation of larger communities. Together these three articles constitute what I call "Community by the Numbers," a theory of community size.
Though I'm going to point to some studies which support these numbers, in general my goal here isn't to try and prove this theory of community size numbers, but rather to lay the theory out completely.
Tightly-Knit Group Thresholds
Groups can clearly exist at any size, from a partnership of two, on upward. However what I'm going to write about here are the threshold values: the ideal numbers where a community seems to function best, and the less than ideal numbers at which a community begins to grow unstable, remaining so until a new threshold number is reached.
I'm also specifically talking about groups that are both tightly-knit and participatory communities. Clearly Ford Motor Company, with 250,000 employees, doesn't match any of these group thresholds. But any self-contained community within Ford probably will (and in fact, it will probably be either a "Working Group" or a "Non-Exclusive Dunbar Group", both terms I'll explain below). Similarly, a non-corporate community that doesn't require everyone to participate won't work quite the same as a community that does require participation from each member (though that's again the topic of the third article in this series).
7, "The Working Group".
This community size probably runs from about 4-9 members, but 7 is a pretty good average, and one that shows up in multiple studies. This number may well relate to the general rule of seven (original paper), which suggests that 7 is a number that the brain can easily and intuitively comprehend.
It has become increasingly clear that a tightly-knit group of 7 is the first group size which is truly an optimal community size. Groups below this size can function effectively, but risk not having enough manpower to deliver a result that everyone is happy with, or having insufficient viewpoints to avoid group think.
Seven is not only an optimal size for a wide variety of corporate and government committees, it is also a healthy size for a small business and even a good size for a party of close friends. More importantly, 7 is a very comfortable group size as it "feels" relatively natural. At this size members find it easy to get to know the other members of the group, and they're able to function well together in a very intuitive and organic fashion.
An interesting example of this group size is the modern infantry
"squad", which consists of two fire teams of 4 people, and a squad
leader, for a total of 9 people. Each fire team is is large enough to
function on its own, but together the group of 9 can still have effective
small group dynamics.
It is typically at this size that the first signs of leadership in a group informally emerge, but the leadership usually isn't overbearing at this level, nor does there tend to be any rebellion against it — perhaps because the group may be too small to elicit multiple leaders.
13—"The Judas Number". A group size of 13 doesn't represent a threshold ideal value, but rather a threshold nadir. It is one of the points where groups can change behavior and risk becoming dysfunctional. There's one of these nadirs beyond every group threshold, where the previously harmonious group dynamics become more difficult. I've chosen to highlight this specific number because it's a point that small communities often hit, particularly as entrepreneurial organizations try to grow above their startup beginnings.
(I should note that 13 isn't a precise number, but rather one offered because it's in the right range and because it's poetically easy to remember. The exact number occurs somewhere between 9 and 25, but I suspect it is worst in the range of 12-15.)
In a group of this community size no one ever feels like they get a fair share of time. Studies show that at this size participants underestimate the amount of time they contributed to the conversation, and thus will come out feeling like they were unfairly ignored despite having a fair share of the conversation. Groups of this size risk people being lumped into categories and ceasing to be trusted as individuals. In addition, problems start with the development of "too many chiefs," yet there is not enough enough variety of non-chiefs for them to direct. Furthermore, multiple leaders may struggle for hierarchical status, increasing the conflict in an already troublesome group.
If your community is unfortunately stuck at this nadir, one of two things usually occurs.
Most commonly, the group shrinks. This could be because participants unhappy with the group dynamics abandon it; or it could occur in a more organized way with the unwieldy large group breaking into two or more smaller groups. For example, a terrible group of 13 could become two more functional groups of 6 and 7.
Alternatively, more energy could be expended. This could be in the form of more formal organization, rewards for participation, or more time to be casual and socialize in order to shake off the tensions of this size group. Though these efforts don't usually change the size of the group, they can improve its dynamics.
Energy could also be spent to help push the group up to the next threshold. Though this could occur naturally — for example if the group focuses on a topic of particular interest that causes new people to continually be added. In addition, in order to grow a group to a new threshold it often requires the efforts of more than one leader to succeed.
A group size of 13 isn't necessarily bad, just more difficult. Anthropological studies show that primitive hunting tribes often temporarily broke into "bands" of this size — my presumption is that the value of having that many people hunting together outweighed the social costs of the group. It is interesting that most juries are made up of groups this size. I believe that the social dynamics of this size of group with all new members creates some tension among the jurors, which may serve justice to make sure that all sides are considered by the jury without falling into groupthink. However, from my experience, the interpersonal conflict in a jury can also slow down the deliberation process and cause much frustration among the participants.
50—"The Non-Exclusive Dunbar Number". More properly this group size falls in the range of 25-75 participants, but it seems to feel the most natural in the range of 50-60. Studies of the sizes guilds in online games support this hypothesis. For instance, based on graphs of the guild sizes in Ultima Online, groups have a median of 61 members. Similar numbers hold true in studies of a more recent game, World of Warcraft.
I call this value the "Non-Exclusive Dunbar Number" because it matches the lower end of a threshold that Robin Dunbar set for group sizes. However, at this size it applies to mostly non-exclusive groupings, which includes the above mentioned online guilds, many employee communities, and the majority of social gatherings that manage to rise above the size of a Working Group. Groups of this size can be serious or take up a lot of time, but in general they are not exclusive — they don't tend to be the only group that individual participants are involved in.
90—"The Dunbar Valley". As Non-Exclusive Dunbar Number communities grow, they reach a point where increased time obligations and the noise of socialization required to keep the group cohesive requires a much more serious commitment from the participants. Like the Judas Number, the Dunbar Valley is a threshold nadir where more energy is required to keep a tightly-knit community together; either the community agrees to a higher level of commitment and grows to the next level, or the community splits apart.
I've found this to be true when growing a small business — where it is too small for any middle-management, but the sub-groups are too large for one person to manage effectively. I've also seen this with more ephemeral groups, such as when a small conference that worked well at 60 participants tries to grow and finds at at 100 participants they can't sustain a high enough intimacy level.
Another illustration of the Dunbar Valley is the history of the ancient Roman "century", a grouping that was originally 100 soldiers. However, as the years went by, centuries tended to decrease in numbers to only include 70 or 80 soldiers. This might well be due to Non-Exclusive Dunbar constraints: even in a very devoted group of military men, there was still the need for relationships with other century groups, with support staff, and with camp followers, ultimately lowering the attention that could be spent on the century itself.
150—"The Exclusive Dunbar Number". Robin Dunbar got much of the discussion of group thresholds started with his article, "Co-Evolution Of Neocortex Size, Group Size And Language In Humans." However, as I've written previously, and as I've described in this article, Dunbar's group threshold of 150 applies more to groups that are highly incentivized and relatively exclusive and whose goal is survival.
Dunbar makes this obvious by the statement that such a grouping "would require as much as 42% of the total time budget to be devoted to social grooming."
The result of the grooming requirement is that communities bounded by the Exclusive Dunbar Number are relatively few. You will find hunter/gatherer and other subsistence societies where this is a natural tribe size. You'll also find these groups sizes in terrorist and mafia organizations.
Clearly, as we step up toward higher group thresholds, more and more
time is required to simply keep the group going. You see this in
depictions of mafia life — in the TV series The Sopranos a lot of time
is spent dining, hanging out, and drinking together. That is part of that 42% social
grooming time required for that intense of a survival group.
It is possible for a large company to force groups up to this size by expending lots of energy (which is to say money) to keep it healthy. Apple did this during the invention of the Macintosh, the first OS X operating system, and the iPhone, but the intensity required of such large teams is not sustainable for long periods of time.
Without that extra energy, few modern tightly-knit communities can reach this threshold, or else can't hold it for very long. Instead they fracture into groups of individual interest (even if they continue to "meet" in the same real-world or online forum), which are more than more likely to be bounded by the Non-Exclusive Dunbar number.
Given the difficulty in even arriving at the Exclusive Dunbar number, it may well be the highest limit of all for a tightly-knit community. Beyond this limit, communities are less cohesive, less trusted, and less participatory (and the topic of my third article in this series.)
Conclusion
There are many different ways to measure groups, and one is by counting its members. As I've discussed here, the number of members can have a huge impact on whether the communities are successful or not. Thus, as community organizers, social software engineers, game designers, or as sociologists interested in community dynamics, we must ultimately consider group thresholds and group nadirs; to understand how to create cohesive communities, rather than groups that fly apart.
In my next article I'm going to talk about thresholds that are personal, rather then group-oriented.
Some other posts about the Dunbar Number and group size issues:
- 2004-03: The Dunbar Number as a Limit to Group Sizes
(also some really good comments)- 2005-02: Dunbar Triage: Too Many Connections
- 2005-03: Dunbar, Altruistic Punishment, and Meta-Moderation
- 2005-07: Cheers: Belongingness and Para-Social Relationships
- 2005-08: Dunbar & World of Warcraft
- 2005-10: Dunbar Number & Group Cohesion
- 2008-11: Community by the Numbers, Part II: Personal Circles
My bookmarks to various papers and websites on this topic are available at delicious.com/ChristopherA under some of the following tags:
- group threshold - everything I have on the topic
- workinggroup - on small groups such as committees
- dunbar number - on larger groups such as tribes
If you have any links on this topic that you would like to share with me, tag them for:ChristopherA and I'll take a look.
Many thanks to Shannon Appecline and F. Randall Farmer for their assistance with this series.
: Only my most favorite songs are rated 5. They have to meet the following criteria: they make me feel good or excite me no matter how often I listen to them, I can typically listen to them often without getting tired of them, and they are the best of their particular genre.
: There is only a small difference between a song that is rated 4 and 5 in my ratings -- typically it doesn't excite me or make me smile quite as much, or it isn't necessarily an exemplar of its genre. However, I still can typically listen to them often without getting tired of them. Items that are rated 4 and 5 are ones that I carry on my iPod Shuffle.
: There are a few songs that I do consider to be great, but that I only want to play when I'm in the mood for them, or I want to only play in a specific order, or they "don't play well" with other music. For instance I love the song "The Highwayman" by Loreena McKennitt, however, it is over 10 minutes long and I just don't want to hear that type of song unless I'm in the mood for it. Other examples are the 12 songs that make up Mussorgsky's "Pictures at an Exhibition" -- I want them played in order when I do play them, and I really don't want them played in the middle of my other songs. Unfortunately, iTunes does not let you select only unchecked items, so I don't have a Smart Playlist for these; instead I keep them in a regular playlist.
: These are songs I like. Typically I can play them regularly but not too often. Songs rated 3-5 go on my iPod Nano.
: There is a lot of music that I think is Good, but I don't want to play all the time. I have a large catalog of sound tracks from movies. All but a few of those tracks are in this category. Again, iTunes does not let you select only unchecked items in a Smart Playlist, so I have several regular playlists for these items.
: I have very diverse musical tastes, starting with jazz, various ethnic and world music, and also including quite a bit of pop, rap, R&B, punk, and metal that I enjoy. I don't enjoy them all the time -- but I do like them to pop up every once in a while for variety. So I rate these 2 and leave them checked. I have an old 40GB iPod that I take on long trips, and it stores everything I have that is checked and rated 2-5.
: Some songs are OK, but I really have to be in the mood specifically for that song. Listening to Jimmy Buffet's "Margaritaville" can be a guilty pleasure on a lazy summer day at the beach, but it isn't something I want to regularly listen to. I have a number of special playlists for songs rated like this.
: These are the songs that I don't like. They're just not my style. Many are still quality music, they just doesn't work for me. I do keep most of these for completeness -- it might just be one or two songs on the album, and I want to keep the album complete. Or I keep it in case my tastes change. But in general, once something is rate 1 Star, I'll probably never listen to it again.
: These are songs that not only do I not like, they just are not good music. I don't like most rap music, but I can tell that most are still quality. Some are junk -- these I rate 1 and uncheck, and are candidates for deletion the next time I purge my collection.
, playcount > 0: If I've listened to something through to the end, but haven't rated it yet, it shows up in this Smart Playlist. Periodically I check this Smart Playlist, sort by playcount, and try to rate everything that I've listened to more then once.
I also try to be aware of Play Count -- this number only goes up if you play a song to the end. So even if I'm not able to take a look at the rating (for instance when I'm in a car), I can at least forward to the next song. Periodically I review the play counts for songs that I've rated and consider moving them up and down accordingly. Of course, this means that I have to be careful and not let the iPod keep running when I'm not listening.
: These have to be the exemplars -- the best books I've ever read, would be glad to read again, would be proud to show off on my best bookshelf, and will buy extra copies to give to friends.
: These have to be really good books -- most of them I'm willing to read again and I promote them by offering to loan them to my more discriminating friends. Although I may keep them on my bookshelf I'd rather give them to a friend then sell them at a used book store.
: These are books are decent books, and I do share them with my voracious reader friends. But I don't push them and I'm much more likely to sell them at a used bookstore then keep them on my shelf. This is the rating that I significantly underused previously, and I'm finding that the key discriminator for me so far is how much I feel like recommending this to friends who are more discriminating readers.
: This rating is where the Amazon rating system fails the most -- these are suppost to be books that "I don't like", however, most of the time I don't buy books that I probably wouldn't like, much less read them, so I have very few in this category. However, I've decided this category is for books that are just not quite good enough, or are slightly disappointing. Not bad, or disliked, but just somewhat disappointing.
: This is where I put the books that I don't like, or worse, I hate. Not many here, but I'm willing to risk more then many people are so I have some. Also books go here that just don't fit my interest, like romance novels that get recommended to me because I like some crossover fantasy-romance authors.
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