Suppose you've got a project that is running late. Is there any proof or argument that teams become much more productive by adding more people? I am looking for answers that can be supported by facts and references if possible.

What I'm thinking about is that existing devs have to teach the new ones (thus losing overall development time), and then the new developers have to study the code (and tasks) before they can become fully productive.

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    Someone always said the following to me: "9 Women can't make a baby in 1 month"
    – RJD22
    Jun 27, 2013 at 11:08
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    – Uooo
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  • There is canonical, well-known literature answering specifically this question. This has been known for years. A simple google search with the exact title of your question will come up with the answer ("The Mythical Man Month") in the top 5 results. Did you try looking before asking?
    – Andres F.
    Jun 27, 2013 at 12:14
  • Why is this always about late-running projects? And what is a project? Can one person do the Accounts Payable and Reveivable project faster than 2? When are parts of a project so different that they're two different apps?
    – JeffO
    Jun 27, 2013 at 23:07

3 Answers 3


Your questions has the answer in it.

Adding man-power to a project that is running late, only makes it worse because the communication overhead increases in a non-linear way.

It's already been studied.

Read "The Mythical Man-Month".

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Fred Brooks in his book The Mythical Man Month discusses this issue.

The conclusion is clear - communication overheads make this a bad idea.

This is known as Brooks' law: "adding manpower to a late software project makes it later".


If the late projects problematic part can be easily isolated - then adding additional resources will help. Adding resources for parallel tasks will complicated things even further

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