Money Illusion

Definition

Money illusion is "a tendency to be influenced by nominal as well as real monetary values in one's thinking about, and the conduct of, economic transactions" — even by people who, at some level, know the real value is what should matter. Shafir, Diamond, and Tversky argue it arises because people hold both a nominal and a real representation of the same transaction simultaneously, and the nominal one is biased to dominate, much as a gains/losses frame can dominate a final-assets frame in prospect theory even though both describe the same wealth.

In the Book

The chapter documents three signatures of the illusion: sticky prices and wages that lag inflation more than pure rational adjustment would predict, the near-absence of inflation-indexed contracts even where indexing would clearly serve both parties, and everyday discourse — newspapers comparing unadjusted salaries or donations across decades, debt-financed projects that sum initial cost and interest into one nominal number — that mixes up nominal and real values. The book draws an explicit parallel to the framing analysis elsewhere in the volume: a choice between a certain $250,000 and an even chance of $240,000 or $265,000, framed as final wealth, gets a different answer than the identical choice reframed as a certain $0 versus an even chance of losing $10,000 or gaining $15,000 relative to a $250,000 reference point — the same duality (final state versus change) that produces money illusion when nominal value stands in for the "final state" and real value doesn't get computed. The persistence of money illusion even in high-inflation economies (the chapter cites Israel's partial dollarization) shows it isn't simply eliminated by experience or necessity.

Why It Matters

Money illusion means nominal numbers carry real psychological weight independent of what they're actually worth, which is why a 2% raise during 4% inflation (a real pay cut) is experienced very differently from a nominal pay cut of the same real size, and why central banks can rely on some resistance to lowering nominal wages even when real wage cuts would clear a labor market. Any policy, contract, or pricing decision phrased in currency should expect people to anchor partly on the number printed, not solely on its purchasing power — the same representational bias prospect theory identifies for gains and losses, applied to the unit of money itself.