Guiding principles in project management: Brooks` Law

Why additional resources are not always helpful

What is Brooks’ Law?

Frederick (Fred) Philips Brooks is an American computer scientist who coined the phrase in his book "The Mythical Man-Month: Essays on Software Engineering":

„Adding manpower to a late software project makes it later. “

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This phrase, which at first seems counter intuitive to any project manager and which Brooks learned from his experience as a software engineer at IBM, became known as Brooks` Law.

Why do projects keep getting delayed when resources are added?

According to Brooks, several reasons are responsible for the further delay of such a project:

1. Onboarding new employees:
The main reason for the further delay is the time it takes to onboard new employees until they can contribute productively to the project. To optimally prepare new employees for their roles in the project, it makes sense for current employees to handle the onboarding, as they possess the necessary expertise. However, while they are introducing their new colleagues to the project, neither the existing nor the new employees can actively work on the project. So, by the time everyone is productive, a lot of time has passed—time that can hardly be made up later. In addition, new employees may make mistakes early on due to a lack of knowledge, which must then be corrected and thus slow down project progress.
On top of that, the new colleagues first have to integrate into the team, which means the team-building phase—which had already taken place at the start of the project—must be repeated.

2. Increased Coordination Effort:
As more employees are added to the project, the coordination effort within the team also increases, since each individual must coordinate with more colleagues. This reduces employee productivity and can thus lead to further delays in the project. To illustrate the increased communication effort, Brooks explained this point in his book using a simple formula. If n employees are working on a project, there are (n²-n)/2 communication interfaces. This means that 2 people have 1 interface, 3 people have 3 interfaces, 4 people have 6 interfaces, and with 10 people, there are already 45 communication interfaces. This makes it easy to see why the communication effort increases exponentially. Simply put: A small number of employees can coordinate while heading to the coffee machine, whereas large teams must organize scheduled meetings to exchange important information. Since time spent communicating is not productive work time, additional capacity is wasted in this way.

3. Indivisible tasks:
At a certain point, tasks can no longer be divided among different employees—or can only be done so with a great deal of coordination effort—because the tasks must be clearly divided and the results subsequently recombined. So if there are more people available than there are assignable tasks, the additional employees cannot help with the work; instead, they hinder rapid progress by creating additional coordination tasks.

4. Additional effects:
It is also important to consider that adding more employees can reduce the team's productivity—for example, because employees may no longer feel as responsible for their tasks or may be less motivated overall.

Generalisation of Brooks` Law

Brooks’ Law originally applied only to software projects. However, since the reasons mentioned above do not apply exclusively to these projects but are generally valid, Brooks’ Law can also be applied universally—not only to employees but also to other resources such as budget or time. For example, it can be said that an additional budget does not necessarily lead to a project being completed faster if the underlying problem is not resolved by the additional funds.
Furthermore, the law can be applied not only to project delays but to all negative outcomes. For example, adding more team members can exacerbate conflicts within the team or lead to poorer product quality.
In general, therefore, it can be said that adding more resources to a project is sometimes not helpful, but rather counterproductive.

Concerns about Brooks’ Law

Brooks himself describes his concept as an extreme simplification, as it does not take into account a wide range of factors that also play a role, for example:

• The current employees, for example, in terms of their ability and willingness to train new colleagues.
• The new employees, for example, in terms of their experience in similar projects or their willingness or ability to learn - for example, a new colleague with a lot of experience can work productively more quickly than a complete newcomer who needs more training time and thus also keeps the existing employees busy for longer.
• The number of staff to be added and the overall size of the team.
• The social dynamics within the team.
• The type of communication within the team.
• The tasks of the project and their divisibility - for example, it may be helpful to bring in new staff to work alongside existing staff and take on simpler tasks such as project documentation.
• The reason why new resources should be added.
• Additional steps to support the project that may be taken in addition to increasing resources.
  Furthermore, Brooks’ Law applies only to projects that are already behind schedule. This means that if a delay is imminent, adding resources may, under certain circumstances, have a positive effect. Furthermore, the reasons for the delay are not taken into account. For example, it may be that the project effort was generally overestimated at the start of the project.

How Brooks’ Law helps in project management

Brooks’ Law provides you with an important insight—namely, that adding more resources to a project is not always helpful. With this insight, you can determine whether a project would truly benefit from additional resources, as well as how many resources should be added and how they should support the project. Keep in mind, however, that Brooks’ Law does not always apply. If a project was planned with too few resources from the outset, or if it involves high-volume tasks that can be processed in parallel, additional resources will actually be helpful.
So before adding resources to a project, you should ask yourself:

• What goals are to be achieved with additional resources?
• How can additional resources support the achievement of objectives?
• How might additional resources jeopardize the achievement of objectives?
• How effective will these and the current resources be then?
• How efficient will these and the current resources be then?

Weigh these questions well against each other. For example, it may be that additional staff will reduce the productivity of individual members of your project team, but still result in higher productivity overall. You may also find that adding many more resources does not make sense, but a few selected resources would help the project.
Furthermore, you should always consider other ways to achieve your goals. For example, if a budget overrun is imminent, you can take measures other than increasing the budget to still complete your project successfully. You can read about the different options in the blog post "Project budget exceeded - and now?" The same applies if you notice that a delay is looming: In addition to additional resources, it may also be possible to extend the project duration or, for example, reduce the project scope.
Our tip: With this type of analysis, you can also verify whether your current project is being executed optimally, or whether you’re using your available resources efficiently and effectively.
If you’re familiar with Brooks’ Law, it can also help you when communicating with stakeholders. In our experience, when a delay looms, calls for additional resources quickly arise. In such a case, you can use Brooks’ Law to explain why adding more resources isn’t a good idea and then work together to find a better solution. If additional resources are added to the project nonetheless, you can identify the associated difficulties more quickly and try to take countermeasures. For example, depending on the circumstances, you may insist on new team members who already have extensive experience with similar projects or who have previously worked with the other team members.

Conclusion

According to Brooks' Law, adding more resources to an already late project can make the delay worse for a variety of reasons. If you are aware of this, you can carefully consider whether you can use new resources wisely to achieve your goals when the project is in trouble, and if so, how many resources you need and how they should be used. This insight helps you find an optimal solution for your project and communicate it to the stakeholders.

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