Campbell's Law - OrgRiver

The more weight an organization puts on a single number, the more that number stops measuring reality and starts replacing it.

2 min read

What Is It?

Campbell’s Law, formulated by social scientist Donald T. Campbell in a 1976 paper on evaluating social programs, states: “The more any quantitative social indicator is used for social decision-making, the more subject it will be to corruption pressures and the more apt it will be to distort and corrupt the social processes it is intended to monitor.” Campbell’s version predates Goodhart’s Law and is more explicit about the mechanism. Goodhart’s Law describes what happens to the measure: once it becomes a target, it stops being a good measure. Campbell’s Law describes what happens to everything underneath the measure: the underlying process the number was supposed to represent gets actively reshaped, sometimes deliberately gamed, sometimes just quietly reorganized, until it produces the number more efficiently than it produces the outcome the number was meant to track. Campbell used the word “corruption” deliberately, but in the broader sense of systematic distortion, not merely fraud or criminal misconduct.

Why Does It Matter?

High-stakes metrics don’t sit passively above an organization, observing it. They reach down into how work actually gets structured. A hospital rated on wait times can improve wait times by changing how patients are logged, not only by treating them faster. A school system rated on standardized test scores can raise scores by narrowing what gets taught to the test, not only by teaching better. Neither requires fraud in the criminal sense. Both are the predictable result of attaching real consequences, funding, reputation, continued employment, to a specific number. The organization isn’t rebelling against the metric. It’s taking the metric seriously enough to reorganize itself around it. The higher the stakes riding on a single indicator, the faster and more thoroughly this happens. A metric quietly tracked with no consequences attached stays a reasonably honest reflection of reality far longer than the same metric turned into a target tied to bonuses, headlines, or survival. Eventually the metric stops representing success and quietly becomes the organization’s operational definition of success: people stop asking whether things actually improved and start asking only whether the number did.

What Changes Once You See It?

You stop treating “the number is high-stakes” and “the number is trustworthy” as compatible facts about the same metric for very long. The two erode each other over time. You start asking not just what a metric measures, but what it would take for someone under real pressure to move it without moving the underlying reality, and how visible that gap would actually be if it happened. You also start favoring designs that are harder to distort: multiple independent indicators that would all have to be gamed simultaneously to produce a false picture, audits that check the process behind a number rather than just the number itself, and consequences calibrated so that no single metric is important enough on its own to justify quietly reshaping the work around it.

Common Misunderstandings

It is not an argument against measurement itself. Campbell was a methodologist who believed deeply in evaluating social programs; the law is a warning about over-reliance on a single indicator, not a case for abandoning indicators altogether.
It is not the same claim as Goodhart’s Law, even though the two are frequently cited together and describe the same failure from different angles. Goodhart’s Law is about the measure’s meaning collapsing once it’s a target. Campbell’s Law is about the underlying process getting actively distorted to serve the measure, a more specific and more corrosive claim.
It doesn’t require anyone to act in bad faith. Much of the distortion Campbell described happens through ordinary, individually defensible decisions made under real pressure, not coordinated cheating.
It isn’t only about extreme cases like outright fraud. The far more common version is quiet, gradual reallocation of effort toward whatever moves the number, at the expense of whatever doesn’t, long before anyone would call it corruption.

Diagnostic Question

If someone under real pressure needed to move this number without improving the underlying reality, could they, and would we notice if they did?

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Origin

Donald T. Campbell, “Assessing the Impact of Planned Social Change,” a 1976 paper for the Public Affairs Center at Dartmouth College, later published in Evaluation and Program Planning in 1979. Campbell’s formulation predates and generalizes the more widely known Goodhart’s Law, which was stated independently by economist Charles Goodhart in 1975.