From a single person to group sizes of over 1000 people, the ideal number of people in any group is becoming quite a science. After some research I have discovered that not only are there some serious thinkers spending quite a bit of time developing this idea, but these thought processes about group sizes have been around in the military for 100’s of years. One thing is certain, adjusting the number of people in a group size, directly impacts the group’s cohesion and performance. How many people are in your groups?

Anthropologist Robin Dunbar found that the MAXIMUM number of people that a person could keep up with socially at any given time, called gossip maintenance, was 150. This doesn’t mean that people don’t have 150 people in their social network, but that they can only keep tabs on 150 people at any given point.

Dunbar’s Numbers

According to Christopher Allen, associate faculty member at Bainbridge Graduate Institute Dunbar’s Number is just one data-point in an overall equation describing which group sizes work and which don’t. Working our way up from the smallest group sizes, I think we can find many break points, both above and below Dunbar’s Number of 150. The smallest viable group size seems to be somewhere in the range of 5 to 9.

Looking smaller, we see that a group of 2 can be tremendously creative (ask any parent), but often has insufficient resources and thus requires deep commitment by both parties. Consider for example the difficulty of a 2-person business partnership which can be compared to that of a marriage. A group of 3 is often unstable, with one person feeling left out, or else one person controlling the others by being the “split” vote.  It is for this reason the Military sends Snipers out in groups of 3. The shooter and the calibrator are teamed as a pair and the third watches out so they don’t get spotted. A group of 4 often devolves into two pairs.
 

What is the ideal number?

Perhaps it is at 5 that the feeling of “team” really begins. At 5 to 8 people, you can have a meeting where everyone can speak out about what the entire group is doing, and everyone feels highly empowered.

According to Christopher Allen there is a study from the 1950s that shows that the optimum size for a committee is 7.
However, at 9 to 12 people this begins to break down - not enough attention is given to everyone and meetings risk becoming too noisy, too boring, too long, or some combination thereof.  Likewise, Allen continues, it’s fairly easy for us to see and agree that a dinner party starts to break down somewhere above 7 or 8 people, as do also tabletop games of both the strategic (I prefer 5) and role-playing varieties (I prefer 7).

The chasm that starts somewhere between 9 to 12 people can be especially daunting for a small business. As you grow past 12 or so employees, you must start specializing and having departments and direct reports; however, the company may not be large enough for this to be efficient, and thus much employee time that you put toward management tasks, is wasted. Only as you approach and pass 25 people does having simple departments and managers begin to work again, as it starts to really make sense for department heads to spend significant time just communicating and coordinating (and as individual departments become large enough to once again allow for the dynamic exchange of ideas that had previously occurred in the original 5-9 member seed group).

Group dynamics improve in efficiency and productivity as you approach 50 which represents the next most optimized group size since size 7.

The next chasm occurs when you go beyond 80 people, which I think is the point that Dunbar’s Number actually marks for a ‘non-survival’ oriented group. Even at this lower point, the noise level created by required social interaction becomes an issue and as you approach 150 this begins to be unmanageable. Once a company grows past 200 you are really starting to need middle-management. The Goretex Company has elected to continue creating new business units when the number of staff grows up to 200. Only when you get up past that, maybe at 350-500 people, does middle-management start really working, primarily because you’ve once again segmented your original departments, possibly again reducing them to Dunbar-sized groups.

Military groups sizes

According to Bruce Schneier  an expert in security, these numbers are reflected in military organization throughout history: squads of 8 to 12 people are organized into platoons (16-44) of three to four squads, organized into companies (62-190) of three to four platoons, organized into battalions(360-1000)  of three to four companies, organized into regiments of three to four battalions, organized into divisions of two to three regiments, and organized into corps of two to three divisions.

Two questions then:

  • Could group sizes be partly to blame for poor productivity?
  • Could re-organizing your work groups into productive number units save you money?

R.I.M Dunbar, “Neocortex size as a constraint on group size in primates,” Journal of Human Evolution (1992), vol. 20, pp. 469-493.
http://www.bbsonline.org/Preprints/OldArchive/bbs.dunbar.html

Dunbar’s numbers
http://en.wikipedia.org/wiki/Dunbar%27s_number

The Science of Dunbars Numbers.
http://www.lifewithalacrity.com/2004/03/the_dunbar_numb.html

Chuck Colson

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