Micah Zarin's Blog

When a measure becomes a target, it ceases to be a good measure

– Charles Goodhart

Look at any setting where people track performance, and you’ll see how one statistic can reshape behavior. Goodhart’s Law captures this shift in a simple rule: once a measure becomes a target, it loses its value as a measure. When we fixate on a single number, we often distort our choices in ways that undermine deeper objectives. Yet it’s not enough to say, “Avoid narrow metrics.” We need to examine why this fixation happens, how it spreads, and what it costs us.

Part of the problem is that single metrics can act as blinders. Instead of probing deeper, we let that one number guide our every move. We change our behavior to serve it, rather than reflecting on the broader purpose. This dynamic shows up in education when students chase high SAT scores. They learn test-taking strategies, cram vocabulary lists, and drill math questions chosen to mirror the exam. These methods may boost the score, but real curiosity can fade. Teachers also feel pressure to align their lessons with the test. Over time, that narrow focus crowds out creative exploration and real-world problem-solving. The SAT becomes the goal, even though it was supposed to measure college readiness.

A similar pattern appears in academic research, where the h-index can dominate discussions about a scholar’s influence. At first, the h-index seems like a balanced way to track both how often someone publishes and how frequently those papers get cited. But if it becomes the main yardstick for career advancement, researchers find ways to pump their citation counts. They split findings into multiple papers or collaborate in large groups that cite each other. The h-index rises, yet the work may not be as bold or far-reaching as it appears on paper. It becomes easy to mistake a high h-index for groundbreaking research, even though it may be more about strategic publishing than genuine discovery.

Why do we keep falling into these traps? One reason is that data can be seductive. We like to see our progress as a tidy graph or a single score we can compare over time. A single figure feels neat and controllable. But any complex goal—whether it’s improving education, expanding knowledge, or running a company—can’t be fully captured by one statistic. Our fixation on that one number narrows our vision. It can lead to short-term boosts and long-term erosion of the very qualities we wanted to nurture. In a corporate setting, for instance, you might see a focus on quarterly revenue above all else. Managers strip away training budgets or sacrifice product quality to make the books look good. Shareholders applaud the rising number, unaware that the talent pipeline and customer loyalty are under strain.

These distortions also emerge because single metrics are easy to manipulate. People do not always cheat outright, but they often look for the most efficient way to maximize the number. This can mean adopting superficial tactics that appear successful. When our chief yardstick is a test score, students memorize facts without integrating them into deeper understanding. When it’s the h-index, academics choose research topics that yield fast citations instead of riskier projects that might spark real breakthroughs. In these ways, a narrow measure stifles variety and blocks long-term progress. We end up with a sleek snapshot that hides cracks we fail to address until it’s too late.

Another subtle factor is the loss of honest feedback. A metric should function like a mirror, reflecting useful information back to us. But a mirror is only helpful if it isn’t warped. Once a measure becomes a target, it gets warped by our collective efforts to inflate it. Any feedback we receive might be misleading. Businesses might see stellar quarterly figures yet ignore a growing wave of customer complaints. Schools might see higher test scores while students struggle with practical tasks or lose the desire to learn. Academic departments might spot rising h-index values without spotting a decline in creative problem-solving. In each case, the metric offers comfort instead of truth.

We can’t solve these problems by throwing out all measures. Data and metrics can be powerful tools. But to use them well, we need balance and a willingness to look beyond a single score. One strategy is to combine several metrics so that no single figure dictates every decision. Another is to reflect on the gap between what the metric measures and what we truly value. We can also rotate metrics over time, so nobody gets too comfortable gaming one particular measure. These steps remind us that numbers are tools for understanding, not absolute ends in themselves.

When it comes to personal or institutional growth, we need to maintain a broader sense of purpose. We should keep asking why the metric matters and where it might fall short. A strong SAT score is good if it reflects solid reasoning and an ability to learn, not just test-savviness. A strong h-index is valuable if it arises from real impact, not from easy citations. By staying curious about what lies behind the numbers, we can catch signs that the metric is drifting away from its original intent. This vigilance helps us guard against the illusions single metrics create.

Thus, Goodhart’s Law is less about dismissing data and more about using it responsibly. It invites us to see metrics as imperfect representations of complex realities. When we lose sight of those complexities and let one number dominate, we feed illusions of success. This trap can tempt anyone—from students trying to look good on college applications, to executives eager to please investors, to researchers chasing prestige. The antidote is awareness. By reminding ourselves that a single figure is never the full story, we stay open to richer forms of progress. We honor the deeper goals that inspired measurement in the first place.