The Scaled Agile Framework (SAFe) implements the Dunbar’s number in Agile programs to decide the upper limit of the ARTs and an effective Agile Release Train consists of 50 - 125 people (5-12 teams). This suggests that ARTs with these many numbers of people can have a stable, effective social relationship. There are industries having larger trains, but it has the disadvantage of restrictive rules, bureaucracy, politics, and unnecessary management layers.
(Before reading this, please have a quick look on the first part of the blog: Dunbar's number: From Prehistory to 21st Century Enterprise)
Agile Release Train is a long-lived, self-organizing team of Agile teams set to deliver some set of values by planning, committing and executing together through program increment (e. g. Maintaining a Cadence). The default program Increment is for 10 weeks, shorter is 8 weeks and longer is for 12 weeks.
Let’s divide the ARTs by the number people that are manageable in those:
50 to 80 - In ARTs with (50-80) people have a well-balanced system, because of minimal leadership, restrictions, and conflicts. All the members of a medium sized (50 - 80) can have clear transparency over what is happening around. What's more, the collaboration among the members is also very high. Many organizations and top notch Agile leaders consider this size as the perfect size, where leaders can lead with alignment, cross-functionality, and self-empowerment. Such as the founder of Virgin, Richard Branson thinks 60 people is the right size for an ART.
150 - There is a factual industry support behind this size of ARTs. Many companies in past have found that ARTs with a few hundred people are the most effective. This is also the biggest size of Dunbar’s layers. That means this is the optimum limit and more than this would be too much to handle the business on a personal level.
There are industries with ARTs over 500 - 1500 individuals. But you may face many big challenges with this kind of teams:
- Cost management is not clear and complex for any event.
- Longer time periods are necessary for all the members of a bigger team to finish the tasks.
- There will be more dependencies to manage - In Scrum, we have the 7 ± 2 technique, that comes from a psychology paper called "The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information". Which demonstrates that there are limits to how much information we can store in our heads. In Scrum teams, it is necessary to keep high bandwidth communication and relationships which become more and more difficult once we pass the magical number of '9'.
- The program backlog becomes hard to manage because of the bigger size and many tasks. People may get confused with the priority levels, that would cause ineffectiveness. Also, the queue size of the program increment increases WIP (Work in Progress).
- Alignment, transparency, self-organizing, self-managing, empowerment, cross-functionality things are difficult to implement in such big size teams. Also, the practice of continuous improvement is only possible when the relationships in the team display the willingness to take ownership of their problems and solve together, which usually do not happen with bigger teams due to lack of communication and connection.
What the Prominent researchers say about Dunbar’s number:
- Malcolm Gladwell mentioned Dunbar number in his book “The Tipping Point”. He did case studies on a company called W. L. Gore and Associates, now known for the Gore-Tex brand. By doing trial and error on the leadership approaches, he found, if more than 150 representatives were cooperating in one building, distinctive social issues could happen.
- Anthropologist H. Russell Bernard and Peter Killworth have done a variety of field studies. They found their conclusive size limitation to be 290, which is roughly double of Dunbar's. Their estimation of the maximum size of a person's social network is based on a number of field studies using different methods in various populations. But the Bernard–Killworth number has not been popularized as widely as Dunbar's.
References:
http://www.theagileelephant.com/dunbars-number
http://www.scaledagileframework.com/agile-release-train/
https://www.fullcontact.com/blog/maintaining-relationships/
