Sample frameDay 283·Product · Delivery

The project is six weeks late and the obvious answer is three more engineers. That answer has a name, and it's a law.

Product.

Brooks's Law

5 min read·Apply by lunch

The question

Think about the last project that ran late on you: when the extra people arrived, who stopped doing their own work in order to bring them up to speed, how many weeks went by before the newcomers were producing more than they were consuming, and did anyone put either of those two costs on paper before the decision got made?

The idea

Fred Brooks managed the development of IBM's OS/360, one of the largest software projects anybody had attempted, and then spent decades explaining what it had cost him — most of them at the University of North Carolina at Chapel Hill, where he founded the computer science department in 1964. The Mythical Man-Month, published in 1975, is that explanation, and the title carries the argument. A man-month is a unit that assumes people and time trade against each other freely, and they only do that when a task can be split among workers who never need to speak. Brooks's examples of the genuinely splittable are reaping wheat and picking cotton. Software isn't either of them. From that he drew the law: 'adding manpower to a late software project makes it later.' The added burden, he wrote, has two parts. Training: someone already fluent has to teach the newcomers, and they can't do their own work while doing it. Intercommunication: if every part of the job has to stay consistent with every other, the coordination between n people runs to n(n-1)/2 channels. Four people carry six of them. Ten carry forty-five. So three more bodies on a team of seven doesn't buy you three-sevenths more; it more than doubles the conversations that have to happen for the thing to hold together.

The framework

01
Can what's left actually be split?
Brooks's law isn't a ban on hiring. It is a test applied to whatever work is left. He sorts tasks three ways. Some genuinely partition, and his examples are reaping wheat and picking cotton — more hands, proportionally less time, nobody needs to talk. Some can't be partitioned at all however many people you assign, which is where his line about nine months and one baby lands. Most real work sits in between: it divides, but the divisions have to stay consistent with each other, and that consistency is what you're actually buying people for. Write down which of the three your remaining work is before anyone counts bodies.
02
The person who teaches the newcomers is the one you could least afford to stop.
Ramp-up isn't paid by the new people; it's paid by your best ones. Somebody has to explain the domain, the codebase, the decisions already made and the reasons they were made — and that somebody is whoever knows most, which is exactly the person whose output the schedule was relying on. So the first weeks after a rescue hire run backwards: capacity falls before it rises. None of that is an argument against hiring. It's an argument for knowing the shape of the dip and where it lands relative to the date you're trying to save.
03
Every extra person is a set of conversations, not a pair of hands.
The n(n-1)/2 arithmetic is the part that surprises people. Four people carry six channels, ten carry forty-five, twenty carry a hundred and ninety. Output grows at best in a straight line while coordination grows on a curve, so past some size an extra person makes the team slower rather than faster. The way out isn't fewer people, it's fewer channels: sub-teams with one defined interface between them, and a small group holding the decisions about what the thing is. Brooks called that conceptual integrity and argued it comes from few minds — the larger the team, the more deliberately somebody has to defend it.
04
Move the date, the scope or the quality — those are the three levers left.
When a project is late, four things could give: the date, the scope, the quality, and the number of people. Brooks's contribution is to strike the fourth off the list once the deadline is close, which leaves three honest conversations instead of one illusion. You already know how to slice a release so a customer can still get through a thinner version of it, and this is the week that skill earns its keep. Be careful which corner you cut, though: shortcuts taken to save a date don't vanish, they get charged back release by release, and the technical debt frame later on prices that properly.

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