Kahneman, Tversky, and the Asymmetry of Gains and Losses

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Ask someone to choose between a certain gain of fifty dollars and a coin flip that pays a hundred dollars or nothing, and most people take the certain fifty. Ask the same person to choose between a certain loss of fifty dollars and a coin flip that costs a hundred dollars or nothing, and most flip the coin. Standard expected-utility theory, built on a single smooth utility curve, struggles to explain why the same person becomes risk-averse for gains and risk-seeking for losses in a way that flips so sharply. Daniel Kahneman and Amos Tversky's 1979 prospect theory offered a different account: people do not evaluate outcomes against some fixed absolute standard but against a reference point, usually the status quo, and they feel a loss relative to that point roughly twice as intensely as an equivalent gain. That single asymmetry, loss aversion, turned out to explain far more than laboratory coin flips. It predicts why investors hold onto losing stocks too long hoping to break even, why homeowners set asking prices anchored to what they originally paid rather than current market value, and why a small monthly premium against a rare catastrophic loss feels worth paying even when the math says it usually isn't. Kahneman received the Nobel Memorial Prize in Economic Sciences in 2002 for this body of work; Tversky, who died in 1996, was ineligible under the prize's rule against posthumous awards.