The Sunk Cost Fallacy: Why We Throw Good Money After Bad (And How to Stop)
You have been sitting through a terrible movie for over an hour. You are not enjoying it. You could leave and do something far more pleasant. But you stay, telling yourself: "Well, I already paid for the ticket."
This simple scenario captures the sunk cost fallacy — one of the most pervasive and costly cognitive biases in human decision-making.
What Is the Sunk Cost Fallacy?
The sunk cost fallacy occurs when we continue a behavior or endeavor because of previously invested resources — time, money, effort — rather than evaluating whether continuing is worthwhile based on future outcomes.
A sunk cost is any past expenditure that cannot be recovered regardless of what you do next. The key insight: rational decision-making should be forward-looking. What you have already spent is, by definition, unrecoverable.
Why We Fall for It
Loss Aversion
Humans feel losses roughly twice as intensely as equivalent gains. Abandoning a failing project feels like confirming a painful loss. By continuing, we postpone the moment the loss becomes "real." See our guide on loss aversion.
Commitment and Consistency
Once committed to a course of action, we feel enormous internal pressure to follow through. Abandoning a project feels like admitting we were wrong.
Waste Aversion
Our aversion to "wasting" what we have already spent leads us to invest even more into losing propositions. We would rather waste future resources than accept that past resources were wasted.
The Emotional Investment Trap
Beyond money and time, we invest identity, hopes, and ego. The more emotionally invested, the harder it is to walk away.
Real-World Examples
The Concorde Fallacy
The British and French governments continued pouring billions into the Concorde supersonic jet long after it became clear it would never be commercially viable. The term "Concorde fallacy" has become synonymous with the sunk cost trap.
Business and Startups
A founder who has spent two years building a product may refuse to pivot even when market feedback is devastating. Kodak's refusal to abandon film technology despite the digital revolution reflects sunk cost reasoning at an institutional level.
Relationships
"We have been together for seven years — I can't just throw that away." The time spent together is a sunk cost. The only relevant question is whether the relationship will bring fulfillment going forward.
Career Decisions
A professional who spent six years earning a law degree may persist in a legal career they dislike because switching would feel like "wasting" their education.
Everyday Purchases
- Finishing a meal you are too full to enjoy because you paid for it
- Continuing to read a book you dislike because you are halfway through
- Keeping clothes you never wear because they were expensive
The Science Behind Sunk Cost Reasoning
In their landmark 1985 study, Hal Arkes and Catherine Blumer showed that participants who paid full price for theater tickets attended more performances than those who received a discount — even with similar enjoyment levels (Arkes & Blumer, 1985).
Richard Thaler (1980) introduced "mental accounting" — the tendency to treat money differently depending on its mental "account," helping explain why we treat sunk costs as ongoing obligations.
Barry Staw (1976) showed that decision-makers who felt personally responsible for an initial investment were significantly more likely to allocate additional resources to a failing project.
How to Overcome the Sunk Cost Fallacy
Apply the Clean Slate Test
Ask yourself: "If I were starting from scratch today, with no prior investment, would I choose this option?" If no, your involvement is likely driven by sunk costs.
Focus on Opportunity Cost
Every resource you spend continuing a failing endeavor cannot be spent on something better. Ask: "What else could I do with these resources?"
Set Pre-Commitment Decision Points
Before beginning any investment, define clear criteria for when you would walk away.
Seek Outside Perspectives
People without personal investment can evaluate your situation far more objectively.
Reframe "Quitting" as Wisdom
Strategically abandoning a losing course of action is not failure — it is intelligent resource management.
For debiasing strategies and exercises, visit our sunk cost fallacy page.
Related Cognitive Biases
- [Loss aversion](/bias/loss-aversion) — The root cause underlying sunk cost reasoning.
- [Status quo bias](/bias/status-quo-bias) — Combined with sunk costs, makes us doubly resistant to change.
- [Endowment effect](/bias/endowment-effect) — Makes us cling to investments simply because they are "ours."
Conclusion
The sunk cost fallacy causes individuals to stay in failing relationships, professionals to persist in wrong careers, and businesses to pour resources into doomed projects. The antidote is to separate the lessons of the past from the costs of the past. Every moment is a new decision point. The only question that matters: given where I am now, what is the best path forward?