What the data actually shows
The concept comes from psychologists Pauline Clance and Suzanne Imes, who first described the 'impostor phenomenon' in 1978 based on their work with high-achieving women who, despite external success, felt like intellectual frauds and attributed their achievements to luck or error rather than ability. The term and the pattern have since broadened well beyond that original sample.
A 2020 systematic review by Bravata and colleagues in the Journal of General Internal Medicine pulled together the available studies and found that prevalence estimates ranged enormously — from a minority to, by some measures, the large majority of those studied — precisely because there is no single standard way to measure it. The review concluded that the experience is common, appears across genders rather than being confined to women, and is frequently reported among high achievers and in demanding fields.
What the evidence does not support is a precise headline number. The honest summary is that impostor feelings are widespread and well documented, that they show up across many groups, and that the wide spread in the figures reflects measurement differences more than real disagreement about whether the experience is common — it clearly is.
Why this feels different from how it actually is
Impostor feelings thrive on an information gap: you experience all of your own doubt, preparation, and near-misses from the inside, while seeing only other people's composed exteriors. So you compare your private uncertainty to their public confidence and conclude that you are the only one faking it — when, statistically, many of the people around you feel the same way and are equally invisible to each other.
Success can paradoxically intensify it rather than resolve it. Each new achievement raises the stakes and the visibility, so instead of feeling more secure, people often feel they have more to lose and more chance of being 'found out.' This is why it clusters among high achievers: the feeling tracks the gap between external success and internal certainty, and that gap can widen as you accomplish more.
Because almost no one says it out loud, the silence is self-reinforcing. Admitting you feel like a fraud feels risky, so people hide it — which leaves everyone privately assuming they are the exception. The experience is common precisely in the way it is invisible: widely felt, rarely spoken, and therefore easy to mistake for a personal anomaly.
What the research says to do about it
One of the most consistent correctives is simply naming it and learning how common it is. Clance and Imes's original work, and much that followed, found that recognising the pattern — understanding that the feeling of fraudulence is a known, widespread experience rather than evidence of actual incompetence — reduces some of its grip, because it reframes the feeling as a familiar glitch rather than a verdict.
Talking about it appears to help for the same reason. Because the experience is sustained partly by silence and the assumption that you are uniquely affected, hearing capable peers describe the same doubts tends to deflate it. Mentorship and candid conversation about the gap between feeling and competence are commonly recommended on this basis.
Separating the feeling from the evidence is the other recurring suggestion: looking at the actual record of your work rather than the internal sense of fraudulence, and treating success as data about ability rather than reinterpreting it as luck. The research here is more descriptive than prescriptive, so these are reasonable, well-aligned strategies rather than proven cures.
What the research says does not help
Waiting to feel fully qualified before acting tends to backfire, because impostor feelings do not reliably resolve with more accomplishment — they often persist or grow alongside it. Treating the feeling as a signal to hold back can mean indefinitely deferring things you are, in fact, equipped to do.
Trying to out-achieve the feeling rarely works for the same reason. Because the experience tracks the gap between external success and internal certainty rather than your actual competence, piling up more credentials often just raises the bar and the stakes, leaving the fraud feeling intact at a higher level.
Treating impostor feelings as a formal disorder to be diagnosed and cured can also mislead, since it is not a clinical condition. That said, when self-doubt is severe, persistent, and tied to anxiety or low mood that affects daily life, that broader distress is worth taking to a qualified clinician — the impostor label itself is not the right frame for that.
Real numbers in context
The most cited figure is a soft one: across the studies pulled together in the 2020 systematic review, prevalence estimates ranged widely, with some measures putting the share who experience impostor feelings at a majority of those studied. Because there is no standard way to measure it, that range is the honest answer — common, but not pinnable to a single precise number.
Two facts about the concept matter as much as any percentage. It was first described by Clance and Imes in 1978, and the later evidence finds it appears across genders and is especially common among high achievers and in demanding fields — not confined to any one group. And it is not a clinical diagnosis, which means the experience is real and widespread without being a medical condition.