The Ideal size for a software development team is 3.5 people.
In a team of three people , everyone is always working hard , the team leader is still writing lots of code and synchronization is easy.
However, there is always a feeling that we are scarifying long term efficiency for short term results. If only we had one more person in the team !
In a team of four people , there is one guy who is not fully utilized because he is waiting for others, or because he is not feeling the pressure.
The team leader writes less code, as he spends more time on administration and coaching.
As a result, It is easy to conclude the ideal team has 3.5 developers. However, splitting programmers and getting some output is quite hard.
A good compromise is to have three seasoned developers and one fresh out-of-college developer.
The experienced members realize they still carry most of the weight, while the young developer has to prove herself.
This combination also allows the team to work on refactoring and important long term missions,while ongoing bugs are done by the fresh coder.