Originally posted by umop-apisdn:

If you double the size of the crew building a house, you can double the speed the house is built... because constructing a house is a simple process with known parameters.

Doubling the size of a software development team will actually reduce productivity for a time, as the new members "get up to speed" with the codebase, learn internal conventions, etc... often interrupting the more senior staff with questions.

To be honest, a complete stall is likely to occur if you add too many new team members at once, later in production. Assuming you can avoid that, it can still take months just to get back to previous productivity levels, nevermind get "faster" at anything.

The new members were added like a year ago. If they're not up to speed, something is wrong.