The Mythical Man-Month

Fred Brooks wrote The Mythical Man-Month about the lessons learned as the senior software engineer behind OS/360, at the time the slickest operating system ever written.

What became known as Brooks’ Law states, “Assigning more programmers to a project running behind schedule will make it even later, due to the time required for the new programmers to learn about the project, as well as the increased communication overhead. When N people have to communicate among themselves (without a hierarchy), as N increases, their output M decreases and can even become negative (i.e. the total work remaining at the end of a day is greater than the total work that had been remaining at the beginning of that day, such as when many bugs are created).”

He also noted:

  • To make a user-friendly system, the system must have conceptual integrity, which can only be achieved by separating architecture from implementation.
  • To avoid disaster, all the teams working on a project should remain in contact with each other in as many ways as possible (e-mail, phone, meetings, memos etc.) Instead of assuming something, the implementer should instead ask the architects to clarify their intent on a feature he is implementing, before proceeding with an assumption that might very well be completely incorrect.
  • Brooks muses that “good” programmers are generally 5-10 times as productive as mediocre ones.

Brooks’ Law seemed both whimsical and radical back in ’75. It didn’t seem right that adding people to a project would slow it down. A programmer told me it was like a woman having a baby in nine months; it didn’t mean nine women could not produce baby in one month. Brooks was saying more that that. He recognized that the output of knowledge workers was not directly related to the hours they worked.

Today we recognize that a great knowledge worker may produce as much value as a hundred of her less gifted peers.

Schools may mix the student with off-the-charts promise with his average classmates to avoid the appearance of favoritism.

In business, it pays to devote special attention to superlative performers.


Knowledge workers can goof off and still be productive.

Factory workers, particularly those on production lines, produce the same amount of value each hour. Most manual labor is similar: the best performer may produce 125% of the norm, but never 500%. Managers were lulled into equating hours and output. An employee who knocked off work early was presumed to be a slacker. Kibitzing in the coffee room was regarded as downtime.

Knowledge work is different. Google recruiters figure a top engineer can produce two hundred times more value than the norm! Assume that top engineer sits on a beach for six months and then, in the course of a few minutes, comes up with Google’s new $5 billion innovation?