On the optimum size of your club

This article from The Agile Elephant gives us a lot of clues as to the optimum size of our club.

The research comes from the anthropologist Dunbar. When looking at human organisation he found certain scales of organisation reoccurring.

  • Core group – up to 5 people (family)
  • Close Group – c 15 people (close kinship group)
  • Acquaintance Group – c 50 people (band of related close kin groups)
  • Personal Social Group – c 150 people (bands of common lineage – typical size of a human small village through the ages, and what Dunbar believes is the biggest group of people one Human can have close personal relationships with)
  • Clan or similar organisational entity – c 450-500 people (cohesive sub tribal unit)
  • Tribal Group – c 1500 – 2000 people (a tribe)

Dunbar argues that 150 would be the mean group size only for communities with a very high incentive to remain together.  For a group of this size to remain cohesive, Dunbar speculated that as much as 42% of the group’s time would have to be devoted to social grooming.  Thus, only groups under intense survival pressure such as subsistence villages, nomadic tribes, and historical military groupings, have, on average, achieved the 150-member mark.  Moreover, Dunbar noted that such groups are almost always physically close: “… we might expect the upper limit on group size to depend on the degree of social dispersal.  In dispersed societies, individuals will meet less often and will thus be less familiar with each other, so group sizes should be smaller in consequence.”  Thus, the 150-member group would occur only because of absolute necessity—due to intense environmental and economic pressures.

We could imagine the next level – let’s say that the sense of urgency is lower among neighbours so that you collaborate on household level. If you have 150 accounts in the club system, and the average household is, say 2,5, then the number of individuals (including children) rises to 375. This number starts to rise up to the Clan size.

The Tribal group, interestingly, corresponds to voting districts of the smallest size ( elating to walking distance to a polling station). Read more here.

Of course, the club’s aim might be to exert influence on people around them. Some research suggests that at 25% of any group, a tipping point is reached where, given the right circumstances, the whole group can suddenly change. Read more here.

Agile Elephant
Dunbar, R. (2010). How many friends does one person need?: Dunbar’s number and other evolutionary quirks. Faber & Faber.

Robin Dunbar Website

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