Brooks’s law
Brooks’s law states that adding manpower to a late software project makes it later. It was formulated by Frederick P. Brooks Jr. in The Mythical Man-Month, his 1975 essay collection drawn from his experience managing IBM’s OS/360 project.
The law runs against the intuitive assumption that a late project can be rescued by throwing more people at it. Brooks’s explanation is that software tasks, unlike many physical ones, cannot always be partitioned so that adding workers shortens the remaining time. New team members need time to become productive, and the people training them are drawn away from the work itself, so a project can lose net capacity in the short term even as headcount rises.
The deeper cause is communication overhead. As Brooks put it, when n people must coordinate, the number of communication paths between them grows as roughly n(n-1)/2: quadratically, not linearly, with team size. Every added person increases the coordination burden on everyone already on the team, a cost that offsets, and can exceed, the extra work they contribute. This is the project-management cost-side counterpart of Metcalfe’s law, which frames the same n² scaling as a source of value in a network rather than a source of overhead in a team.
Brooks’s law is not an argument against ever adding people to a project, only against the specific case of adding people to a project that is already behind schedule, where the ramp-up and coordination costs are least affordable. It remains one of the most frequently cited results in software project management.
See also
References
- Brooks, Frederick P. (1975). The Mythical Man-Month: Essays on Software Engineering. Addison-Wesley.