Following up to a discussion I had as an Agile Coach with a team, I painted a simple graph what can be a great food for thought and discussion: what happens if you fiddle with the team size?
In Agile and Scrum utopia teams exists forever and have time and means to improve themselves. They are self-steering so take care of the team as well. In practice, that usually is not the case. Sometimes (in the consultancy project driven world I work in) there are budgets, projects and project managers who guard these. As an Agile coach you’re sometimes caught in the middle when “resources” (they mean: people) are added or removed from teams due to several reasons. To help clarify the effects of this I like to share these thoughts with you.
Startup and sustain periods
When a new team starts (e.g. when a new project starts in the previous mentioned world) a certain “normal” pattern occurs with the team’s velocity. The first 3 or 4 sprints or so, the velocity increases. People get to know each other, the team is getting used to their teammates and the subject matter becomes more known. I call this the startup period. Length may vary depending on the team, the subject matter, the organization, the sprint length, etc.
After that, a period starts I like to call the sustain period. The velocity might go up or down based on the ability to improve, but I like to look at what happens when something is done with the people in the team.