Campbell's Law
The more a quantitative indicator is used for decisions, the more it corrupts the process it monitors.
Donald Campbell, 1979. A sibling to Goodhart's Law (see [goodharts-law]) but with sharper emphasis on social processes. Once teachers are evaluated on student test scores, teachers teach to the test. Once police are evaluated on arrest counts, arrests are produced regardless of actual crime patterns.
The mechanism is universal in any system where humans are measured. The measurement doesn't just lose validity; it actively corrupts the underlying process. The harder the measurement is used for decisions, the worse the corruption.
For operators, Campbell's Law is the deeper version of Goodhart: the corruption isn't just gaming; it's a real reshaping of what people actually do. Worth assuming any heavily-used metric is at least partially compromised.
Examples in the wild
Sales team performance management based purely on quarterly bookings reliably degrades customer quality. The customers acquired to hit numbers eventually churn.
Quarterly earnings pressure famously distorts long-term decisions. Companies cut R&D, defer maintenance, and make worse strategic moves to hit short-term numbers.
Standardised testing pressure produces students who can pass the test, even when they can't reason through novel problems.
Campbell's Law is one of the mental models we apply through real cases inside the Pareto MBA — a part-time program for professionals who want to think clearly about business.