The McNamara Fallacy is named after Robert McNamara, the US Secretary of Defense during the Vietnam War. The fallacy describes making decisions using only quantitative metrics and ignoring anything else.
The fallacy usually follows the same four steps.
Measure what can easily be measured.
Dismiss what can’t be measured easily.
Presume what can’t be measured easily isn’t important.
Extrapolate and conclude that what can’t be measured doesn’t exist.
You can find the McNamara Fallacy in all types of disciplines. The emphasis on standardized tests in education (at the expense of less quantifiable qualities and learning). Or when the success of treatments in medicine is based only on easy to measure outcomes (not quality of life, mental health, or overall well-being). Or optimizing for short-term financial metrics at the expense of brand reputation, employee satisfaction, or other intangibles.