You Can't Manage What You Can't Measure: An Exercise in Logical Fallacy

Photo attribution: Yoichi Okamoto Robert McNamara is known to many as the US Secretary of Defence from 1961 to 1968.  Perhaps more interesti...

Photo attribution: Yoichi Okamoto

Robert McNamara is known to many as the US Secretary of Defence from 1961 to 1968.  Perhaps more interestingly, his name is also infamously linked to a specific error in logic which has become known as the "McNamara Fallacy", a logical fallacy that is unfortunately still blindly applied today via poor management methodology that relies heavily on templating solely quantitative observations without understanding the actual relevance of them.

You may have heard this regurgitated as the maxim "You can't manage what you can't measure", an obsolete business belief rooted in the confusion that fails to comprehend that measurability does not equal relevance.

In McNamara's particular situation, his subscription to this logical fallacy led to the defeat of the United States in the Vietnam War.  McNamara was convinced that victory could be reduced to a metrics based mathematical model and that the abstract of his measurements would enable him to manage a success.  For example, the idea that troop numbers as a purely metric count (soldier vs soldier) could then be applied in a larger context to leverage better training and weapons to win over similar numbers of troops with less training and inferior weapons.

History shows how that turned out, and yet many poor management templates today still make the mistake of subscribing to this mantra.  The common thread in all of them is clear, a confusion between measurability and the actual relevance of those metrics to the problem at hand.

McNamara's subscription to the logical fallacy cost the US the Vietnam War

Expanding on this, the core flaw as I’ve established, lies in the erroneous belief that what can be quantified is necessarily what is important. This dangerous simplification ignores the crucial role of qualitative factors, context, and nuanced understanding. It’s akin to judging the quality of a novel solely by its word count, or assessing the success of a symphony by the number of notes played. Such an approach entirely misses the point, neglecting the artistry, the narrative, the emotional impact – the very essence of the work.

This obsession with quantifiable metrics often leads to a phenomenon known as “metric fixation”, where organisations become so focused on achieving specific numerical targets that they lose sight of the bigger picture. This can manifest in various detrimental ways. For instance, employees may be incentivised to “game the system”, manipulating figures to meet targets without actually delivering meaningful improvements. Or, even worse, they may neglect crucial but less easily measurable aspects of their work, leading to unforeseen consequences and ultimately undermining the organisation’s overall objectives.

Consider, for example, a hospital measured solely on patient throughput. While processing a high volume of patients might appear to be a success according to this metric, it could lead to rushed consultations, inadequate care, and ultimately, poorer patient outcomes. The focus on quantity has come at the expense of quality, demonstrating the inherent danger of prioritising measurability over relevance.

Not understanding what metrics you are measuring can be inherently dangerous when it leads to mismanagement

Furthermore, the McNamara Fallacy often fails to account for the dynamic and complex nature of real-world situations. It assumes a level of predictability and control that rarely exists, particularly in complex human systems. The Vietnam War, as our initial example illustrated, was a conflict fraught with intricate social, political, and cultural factors that simply could not be captured by simplistic metrics like body counts or troop deployments. By reducing the war to a purely mathematical equation, McNamara and his strategists tragically overlooked the crucial human element, the motivations and resilience of the Vietnamese people, and the complex geopolitical landscape of the region.

This same error persists in many contemporary management practices. Businesses may focus obsessively on metrics like website traffic or social media engagement, without truly understanding the underlying drivers of these figures or their actual impact on business outcomes. A high number of website visits, for example, is meaningless if those visitors are not converting into paying customers. Similarly, a large social media following is of little value if it does not translate into brand loyalty or increased sales.

Obsess over the metrics that don't count to your own detriment.
This is surprisingly common in executive circles.

In conclusion, the McNamara Fallacy serves as a stark reminder of the limitations of purely quantitative approaches to management. While metrics can be valuable tools for understanding certain aspects of a situation, they should never be relied upon in isolation. Effective management requires a holistic approach that considers both quantitative and qualitative factors, context, and a deep understanding of the problem at hand. It is not enough to simply measure; we must also understand what those measurements truly mean and how they relate to our ultimate goals. To do otherwise is to risk repeating the tragic mistakes of the past, pursuing the illusion of control while losing sight of the true path to success

For those of you working in a corporate setting Liz Ryan explains this same fallacy beautifully and with appropriate disdain.