What is Sunk Cost Fallacy?
The sunk cost fallacy is the tendency to continue investing time, money, or effort into something because of what has already been spent, rather than evaluating the decision based on future costs and benefits alone. A person who sits through a terrible movie because they paid for the ticket is honoring a past expense that cannot be recovered, rather than cutting their losses and doing something more enjoyable with the remaining time. From a rational standpoint, only prospective costs and benefits should influence a decision, yet people routinely let irrecoverable investments dictate their choices.
How it works
Hal Arkes and Catherine Blumer demonstrated the effect in a 1985 series of experiments. In one study, participants who were told they had paid more for a ski trip were more likely to attend it over a cheaper but more enjoyable alternative, even though neither payment could be refunded. Richard Thaler’s work on mental accounting helps explain the mechanism: people maintain psychological “accounts” for their expenditures and feel compelled to avoid closing an account at a loss. The pain of formally “wasting” a past investment overrides a clear-eyed assessment of what comes next.
Applied example
The British and French governments continued funding the Concorde supersonic jet for years after it became clear the project would never be commercially viable. Billions had already been spent, and neither government wanted to be the one to write off the investment. The phenomenon became so iconic that economists sometimes call the sunk cost fallacy the “Concorde fallacy.” The rational move would have been to evaluate only remaining costs against expected future revenue, but escalation of commitment kept funding flowing.
Why it matters
Recognizing the sunk cost fallacy is essential in product development, organizational strategy, and public policy. Teams that cannot abandon failing projects drain resources from higher-value opportunities. Designing decision checkpoints that explicitly separate past expenditures from forward-looking analysis helps organizations allocate resources based on expected returns rather than accumulated regret.
