Six coders can do anything and there is nothing six coders can't do

In other news, I don't understand why so many people would up-vote a post which is has almost no content and is ostensibly promotional.

In research quoted in Software Estimation by Steve McConnell, for completing a medium sized project (in that research defined as 10,000 to 100,000 lines of code) there was a local minimum of calendar time with teams of 5-8 people. To reach that level of calendar time again you needed a team of at least 20 people. However there is reason to believe that 50,000 lines of code delivered by 20 people will have more duplication of effort and less quality than the same delivered by 5. Which makes the relative productivity of the small team even better.

The reason is simple. The natural loose and open structure of a small team breaks down if the team is too big. Depending on the specific people, it tends to happen somewhere in the range of 6-9 people. Past that you have to manage lines of communication carefully, which results in process and overhead with reduced productivity.

The lesson to draw from this is the following. If you want the project delivered as cheaply as possible, let one programmer work as long as it takes. If you need it delivered quickly you can increase team size to 5-8 people. If you need stuff delivered faster than that you'd better swallow hard, accept a several-fold increase in costs, start hiring, and do careful planning because you'll need it.

(You can pass the small team limit in practice by having different teams on different pieces of software. But they had better be really different. When people have to interact closely, they are part of the same team no matter what the org chart says.)

So yeah, I agree.