McNamara fallacy

The McNamara fallacy (also known as the quantitative fallacy), named for Robert McNamara, the US Secretary of Defense from 1961 to 1968, involves making a decision based solely on quantitative observations (or metrics) and ignoring all others. The reason given is often that these other observations cannot be proven.

This quote by Daniel Yankelovich originally referred to McNamara's ideology during the two months that he was president of Ford Motor Company, but has since been interpreted to refer to his attitudes during the Vietnam War.

Examples in warfare

Vietnam War

The McNamara fallacy is often considered in the context of the Vietnam War, in which he attempted to reduce war to a mathematical model. One example arose in an early 1962 conversation between US Air Force Brigadier General Edward Lansdale and McNamara. Lansdale reportedly told McNamara, who was trying to develop a list of metrics to allow him to scientifically follow the progress of the war, that he needed to add an 'x-factor'; McNamara wrote that down on his list in pencil and asked what it was. Lansdale told him it was the feelings of the common rural Vietnamese people. McNamara then erased it and sarcastically told Lansdale that he could not measure it.

''New York Times'' correspondent David Halberstam wrote about McNamara's fixation on metrics:

Body counts

Another example of the fallacy is the enemy body count metric which was taken to be a precise and objective measure of success. By increasing estimated enemy deaths and minimizing one's own, victory would be assured. Critics such as Jonathan Salem Baskin and Stanley Karnow noted that guerrilla warfare, widespread resistance, and inevitable inaccuracies in estimates of enemy casualties can thwart this formula.

1965 Da Nang visit

David Halberstam wrote of another such incident in which qualitative facts were disregarded due to quantitative bias:

Global War on Terror

Donald Rumsfeld, US Secretary of Defense under George W. Bush, sought to prosecute wars with better data, clear objectives, and achievable goals. Writes Jon Krakauer:

In modern clinical trials

There has been discussion of the McNamara fallacy in medical literature. In particular, the McNamara fallacy is invoked to describe the inadequacy of only using progression-free survival (PFS) as a primary endpoint in clinical trials for agents treating metastatic solid tumors simply because PFS is an endpoint which is merely measurable, while failing to capture outcomes which are more meaningful, such as overall quality of life or overall survival.

In competitive admissions processes

In competitive admissions processes—such as those used for graduate medical education—evaluating candidates using only numerical metrics results in ignoring non-quantifiable factors and attributes which may ultimately be more relevant to the applicant's success in the position.

See also

* List of fallacies – List of Fallacies
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* Newton's flaming laser sword – Verificationist principle
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References

Sources

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Further reading

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{{Fallacies
Inductive fallacies
Metaphors referring to people