Team Size and Faulty Accepted Wisdom

You know that a team should be 5-9 people? Let’s poke holes in that jewel of accepted wisdom.

Let’s start with the idea behind it. It goes like this: as a team grows, the number of lines of communication within the team grows quadratically. Communication becomes so inefficient and expensive that you should avoid having big teams.

What’s a big team? This argument, which has been made everywhere (just Google it), uses math. A team of n people has n(n-1)/2 lines of communication between every member and everyone else. If the team has 5 members, that’s 10 lines. 12 members? It’s 66. And so on. You’ve probably seen a busy-looking star graph accompanying the math.

The problem is, this just doesn’t align with how teams communicate in real life.

If someone has information to share with the entire team, that happens in a meeting, email, or Slack channel. That’s parallel communication, not peer-to-peer.
Team-wide activities (such as planning meetings) happen with everyone present. Communication there is also parallel.
When people need to pull information, they turn to tools and documents, without bugging every member of their team.
If people occasionally collaborate in small groups, updating the entire team about their work still doesn’t happen peer-to-peer.

I fully agree that communication overhead grows with team size, but it doesn’t explode the way this theory says. It grows because more people means greater variety of personalities, communication styles, mental models, attention spans, and availability. As a result, more effort is needed for effective, meaningful communication.

If a certain mission/mandate/project requires 10+ people, and you split them up to smaller teams, the parallel communications I explained above still need to happen. However, the interdependencies between the small teams will require additional communication and coordination, possibly frequently. You might minimize this by having them communicate through point people, such as team lead or PO, but that may produce bottlenecks and a broken-telephone effect.

There’s no magic number for the ideal team size; context is important. I’ve coached successful teams of various sizes, and communication never appeared to be the problem suggested by the communication-lines argument. The more-important factor (and challenge) seems to be that of building trust, safety, and cohesion in a larger team. But that’s for another post.