Picture two scenarios. In the first, your salary rises 2% and inflation is zero. In the second, your salary rises 5% and inflation is 4%. In both cases your purchasing power goes up, but more in the first case than in the second: 2% versus 1%. Even so, when asked, most people say they feel better about the second scenario. This is a systematic error, not an anecdote, and it has a name: money illusion. It means judging money by its nominal figure — the number printed on the page — instead of by its real value, which is what that figure can actually buy once inflation is taken out.
Economist Irving Fisher described it a century ago, and Daniel Kahneman and Amos Tversky later confirmed it in laboratory experiments: the human brain processes numbers before it processes context. It sees “5%” and feels a gain, even though the context — 4% inflation — turns that gain into almost nothing. This isn’t a lack of information. It’s a mental shortcut that fires even when the person perfectly well knows the current inflation rate.
What the money illusion actually is
The money illusion is the tendency to think in nominal terms — the figure on the payslip, the bank balance, the price of a home — instead of in real terms, which are the ones that actually matter because they factor in inflation. A 100-euro note today and one from twenty years ago have the same nominal value but very different purchasing power: what 100 euros buys today would have cost noticeably less in 2006.
The problem isn’t that people don’t know inflation exists. It’s that when making quick decisions — accepting a raise, judging how much a savings account earned, comparing a price to last year’s — the brain uses the number in front of it as the immediate reference point, and rarely stops to recalculate it in real terms. It’s an anchoring bias applied specifically to money: the nominal figure acts as the anchor, and adjusting it mentally for inflation requires extra effort that most people don’t spontaneously make.
The consequences are very concrete. Two people in exactly the same real economic situation can feel — and behave — completely differently depending on how the numbers are framed. And, more importantly, major financial decisions end up being made against the wrong metric.
Why your brain prefers the bigger number
There’s a practical reason and a psychological one. The practical reason is that the nominal number is immediately observable: it’s on the payslip, the bank statement, the price tag. The real number — the inflation-adjusted one — appears nowhere. It has to be calculated, and calculating it requires data (the inflation rate for the period) plus an extra mental step that almost no one runs automatically against every figure they see.
The psychological reason runs deeper. Kahneman described the brain as running two systems: one fast, intuitive and emotional, and one slow, deliberate and analytical. The fast system reacts to the number as presented; only the slow system can adjust that number for inflation, compare scenarios, and reach the correct conclusion. The catch is that the slow system consumes mental energy and only switches on when something forces a second look. Since a raise or an interest rate rarely trips that alarm — they look like good news on their own — the fast system gets the final word.
On top of that sits a framing effect: positive numbers trigger an almost instant positive emotional response, regardless of their real magnitude. Seeing “+5%” produces a feeling of gain before the brain has time to ask “a gain relative to what?” That immediate emotional response is hard to undo afterward, even once the person does run the correct calculation: the first impression, positive or negative, leaves a residue that colors how the rest of the information gets interpreted.
Where it hides in your paycheck and savings
The most common example is salary negotiation. A worker who gets a 3% raise in a year with 4% inflation has, in real terms, suffered a 1% loss of purchasing power. Yet plenty of behavioral economics studies show that same worker reports feeling satisfied with the raise, while a nominal pay cut — even one that produces exactly the same real loss — triggers far stronger resistance. Companies know this, which is why, during periods of high inflation, they prefer below-inflation raises over freezes or nominal cuts: they generate less conflict, even when the economic outcome for the employee is similar or worse.
Something symmetrical happens with savings. A savings account paying 2% while inflation runs at 3% is losing real value every year, even as the nominal balance grows. Many savers check their statement, see the number has gone up, and conclude they’re “earning money.” In reality, they’re quietly losing purchasing power — something that only becomes visible when comparing what that money could buy five years ago with what it can buy today. It’s the same mechanism that makes holding cash, unindexed and uninvested, feel safe when it’s actually one of the most reliable ways to lose value over the long run.
The effect on housing and debt
The money illusion also distorts how people perceive major assets and major debts. When a home’s price rises 40% over ten years, it looks like a spectacular gain. But if general prices rose 25% over that same period, the real appreciation is much smaller than the headline suggests, and in some cases can be close to zero once maintenance costs, taxes and renovations are factored in too.
Debt works the other way, and here the money illusion can actually work in the borrower’s favor. A fixed-rate mortgage signed before a period of high inflation becomes, in real terms, cheaper over time: the nominal payment doesn’t change, but the salary used to pay it does grow nominally with inflation, so that same payment represents a shrinking share of income each year. It’s one of the few situations where failing to adjust for inflation benefits the person making the decision — though few people choose it consciously for that reason; it’s almost always a side effect, not a deliberate strategy.
Why institutions lean on it
The money illusion isn’t just an individual error: it’s a mechanism that institutions and markets build into how they communicate figures, whether deliberately or not. Central banks almost always prefer generating moderate inflation over forcing nominal wage or price cuts, precisely because social resistance to a nominal decrease is far stronger than resistance to an insufficient increase. This preference — documented in the “inflation target” policy most central banks follow, typically around 2% a year — leans in part on the same bias that makes a 3% raise feel better than a freeze, even when the real outcome is similar.
Financial product providers do something similar when they advertise “historical” or “gross” returns without mentioning the period’s inflation, or when they compare a fund’s price today to its value twenty years ago without adjusting for what that earlier figure was actually worth. This isn’t necessarily misleading in a strict sense — the nominal figure is accurate — but it deliberately appeals to the fast thinking system, the one that reacts to the number as it stands, without calculating what that number actually means.
How to think in real terms
Correcting for the money illusion doesn’t require advanced economics, just one concrete habit: before judging any meaningful financial figure — a raise, an investment’s return, a savings account’s interest, an asset’s appreciation — subtract the inflation for that period. If your salary rose 4% and inflation was 3%, your approximate real gain is 1%, not 4%. If an investment returned 7% in a year with 5% inflation, your real gain is closer to 2%.
It also pays to be wary of comparisons that only use nominal figures over long stretches of time — “this home is worth double what it was fifteen years ago,” “my salary has tripled since I started working” — because without adjusting for inflation, these comparisons say much less than they appear to. A simple way to build the habit is to fix a stable mental reference point, such as the consumer price index (CPI) published each month, and use it as an automatic filter before drawing conclusions from any money figure that changes over time.
Finally, it helps to remember that real value is the only one that ultimately matters: not what the number says, but what that number actually lets you buy. Internalizing that distinction, and applying it systematically, is one of the highest-return corrections you can make to how you think about money, precisely because it costs very little effort and protects you from decisions made on the basis of a figure that doesn’t mean what it appears to mean.
