Brooks's Law

Brooks’s Law challenges the belief that a software development effort is perfectly divisible among people. In reality, adding a person to a project incurs training costs and increases the number of communication paths. This can outweigh that person’s contribution for a while.

If a project is already late, adding new developers can cause further delays as they learn the system and may introduce new bugs. Brooks illustrated this with the observation that “the bearing of a child takes nine months, no matter how many women are assigned.” The law doesn’t say adding people never helps, but as a response to lateness, it’s usually counterproductive.

• Simply throwing more developers at a project that's running behind schedule usually slows it down further initially.
• New people take time to get up to speed, consuming existing team members' time for training and coordination, which reduces overall productivity.
• Instead of hoping manpower will solve slippage, adjust the scope or timeline. Be wary of 'just hire more coders' as a solution to lateness.