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Is Five the Optimal Team Size?

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There have been a lot of discussions and debates over the optimal team size for maximum productivity. While most Agilists agree that smaller teams are more functional and productive as compared to larger teams however, defining the optimal team size is still a challenge.

Jeff Sutherland shared some statistics in favor of smaller teams where, the cost per function point of a team of size 7 was $566 and that of a team of size 14 was $2970. On similar lines, in response to a post on InfoQ, about team growth and productivity, Mishkin Berteig commented that

Imagine that you have just been "given" a software development group consisting of 100 developers. Now imagine that you are given a really important project to work on. Which would be better:

a) Get all 100 people working on the project (with good project management, leadership etc.), or...

b) Find the 7 strongest people in the group who are willing to work on the project (in other words, the seven strongest people that are actually interested in the project) and get them working on the project, fire the rest of them, and spend the savings on giving the 7 people the absolute best tools and environment they need and want, and spending the rest to make them happy/comfortable.

Personally, despite the severity of scenario b), I would definitely bet on it and not on scenario a).

Jurgen Appelo suggested that the optimal team size might just be 5. Five is the common number based on various studies around communication and team structures.

  • According to Congnitive Edge, the human brain has co-evolved with social conditions and there is a natural limit on the number of social relationships a person can maintain. The study could easily be labeled as the rule of 5,15 and 150. 5 is linked to the natural limits of short term memory, 15 is the natural level of deep trust and 150 is the number of identities that a person can maintain in his head.
  • Another study related to the Parkinson’s Law, suggested that any team size below 20 can work except 8. Above 20 there is a natural digression into subgroups and no consensus can be formed. With 8, people usually find themselves in deadlock situations over decisions.

Further adding suppoprt for a team of 5 with a  comment on the Parkinson’s Law, PMHut suggested that

The more team members you have, the more communication channels you will have, and this thing goes exponentially. If you have 3 team members, then you will have 4 communication channels, if you have 4 then you have 9. I think the formula is m-1^2.

In my opinion, a small team of 4 or 5 is ideal.

Hence, given the above facts and studies a team size of 5 seems to satisfy all the conditions related to Scrum recommendations, Parkinson’s Law, natural limit of short term memory and favorable communication channels.

However, inspite of strong evidence in favor of a team of 5, Jurgen cautioned that instead of going with a recommendation on team size, the teams should first try to self organize and gradually arrive at an optimal team size. According to him,

When you need to structure a big project, don’t impose a “preferred” team size on people just because it is written in a book. Try to allow self-organization to do its job and let the people (within their real environment) figure out what their optimum is. Do they want to cut a team of seven into two teams of three and four? Sure, why not? Are they merging two teams into one big team of fifteen? Fine, let them see if that works.

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