The Tipping Point: How Little Things Can Make a Big Difference

by Malcolm Gladwell

military planners have arrived at a rule of thumb which dictates that functional fighting units cannot be substantially larger than 200 men,” Dunbar writes. “This, I suspect, is not simply a matter of how the generals in the rear exercise control and coordination, because companies have remained obdurately stuck at this size despite all the advances in communications technology since the first world war. Rather, it is as though the planners have discovered, by trial and error over the centuries, that it is hard to get more than this number of men sufficiently familiar with each other so that they can work together as a functional unit.” It is still possible, of course, to run an army with larger groups. But at a bigger size you have to impose complicated hierarchies and rules and regulations and formal measures to try to command loyalty and cohesion. But below 150, Dunbar argues, it is possible to achieve these same goals informally: “At this size, orders can be implemented and unruly behavior controlled on the basis of personal loyalties and direct man-to-man contacts. With larger groups, this becomes impossible.”

FAST Agile - Dunbar's number for tribe size