Decoy Effect
What is Decoy Effect?
The decoy effect is when adding a clearly inferior third option nudges shoppers toward a specific one of the two original choices.
Also called asymmetric dominance, the decoy is worse than one option in every way but only partly worse than the other, making the target option look like a bargain by comparison. Because people judge value relatively rather than absolutely, the decoy shifts the share choosing the targeted product, even though a rational chooser would ignore an option no one buys. Subscription pricing and menus exploit it heavily.
Decoy Effect: a worked example
A cinema sells popcorn in two sizes: small, 4 ounces for $3.50, and large, 12 ounces for $7.00. Sixty percent of buyers take the small, so average spend is 0.6 x $3.50 + 0.4 x $7.00 = $4.90. The cinema then adds a medium, 8 ounces for $7.25. Nobody should want it, since the large is both bigger and cheaper. Shares move to 25 percent small, 5 percent medium, 70 percent large. Average spend becomes 0.25 x $3.50 + 0.05 x $7.25 + 0.70 x $7.00 = $6.14. The size almost nobody bought added $1.24 per customer.
The mistake students make with decoy effect
People assume the decoy is there to sell, or that any third option lifts the target. Neither is right. The medium in the example is built to be refused; its only job is to make the large look generous beside something worse. Direction matters too. The decoy has to be beaten outright by the option you want chosen and beaten only partly by the other one. Put an 8-ounce tub at $4.00 on that menu instead, at 50 cents an ounce against the large's 58 cents, and you pull buyers away from the large rather than toward it.
Decoy Effect questions
What is the decoy effect in pricing?
The decoy effect in pricing means adding a deliberately unattractive option to a menu so a targeted option looks better beside it. The decoy is specified so the target beats it on every attribute, while the cheap alternative beats it on only some. Sellers use the trick because buyers rank options against each other rather than against any absolute standard of value, so a bad third choice reshapes the comparison.
What is the difference between the decoy effect and anchoring?
The decoy effect and anchoring both plant an irrelevant reference point, but they operate differently. Anchoring uses a single number, often a crossed-out original price, to shift what a buyer believes the item is worth. The decoy effect adds an entire option to the choice set and works through dominance: the target beats the decoy on every dimension, so picking the target feels justified rather than merely expensive.
Why does the decoy effect violate rational choice theory?
The decoy effect violates the independence of irrelevant alternatives, a standard axiom of rational choice. That axiom says the ranking of two options should not change when a third option that nobody selects is added to the menu. In the popcorn example the small beat the large for most buyers, then lost to it once a medium arrived that almost no one bought. The preference reversed with neither original item changing.
Related terms
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