March 25, 2015

The Mythical Man-Month (Worth Reading Again)

  —The Mythical Man-Month and the #NoEstimates debate.

The blog post “Estimates? We Don’t Need No Stinking Estimates!” was passed around my software team. It contains a reference to Frederick Brooks’ essay “The Mythical Man-Month”. As far as No Estimates is concerned, I like Mike Cohn’s view in “Estimates are Not Commitments”.

The reference to Brooks prompted me to review his essay and the wonderfully insightful wisdom contained therein. On introducing Brooks’ Law, Brooks writes:

Oversimplifying outrageously, we state Brooks’s Law: Adding manpower to a late project only makes it later.

People are often familiar with Brooks’ Law but are unaware of the other insights contained in The Mythical Man-Month.

Brooks describes an optimal schedule as one that uses as many people as there are independent tasks. He warns that one cannot obtain a workable schedule using more people or fewer months.

He tells us the man-month is a dangerous measure. It is dangerous because people and man-months are not interchangeable on most projects. It is also a poor measure of progress. Task partitioning, the cost of communication and overly optimistic estimates are important to keep in mind.

The key recommendation is to renegotiate the schedule without adding people and to do so that renegotiation needn’t happen again. This is ideal, but may not be practical because of commitments that require delivery at a specified time. For a look at what insight Brooks has to offer on schedules read Hatching a Catastrophe.

To think of Brooks’ Law in the manner oft quoted is to do a gross disservice to the wisdom within this essay. That is a point worth remembering the next time you are faced with poor effort estimates.