EffectTime & commitment · Cognitive Bias · Entry 223
Sunk Cost Effect – when past costs influence the next choice
Sunk Cost Effect is the tendency for money, time, or effort that cannot be recovered to influence what you choose next, even when the future costs and benefits should be enough to make the decision.
Where can it show up?
- Projects – a team wants to continue mainly because it has already spent a large budget or many months on the work.
- Purchases and subscriptions – you keep using something you no longer value because you already paid for it.
- Personal plans – you stay with a course of action because stopping would make earlier effort feel wasted.
A better check
- Separate what is already gone from what you still have to spend.
- Ask what you would choose today if the past investment belonged to someone else and could not be recovered either way.
- Compare the future value of continuing with realistic alternatives for the remaining time, money, and attention.
- Do not assume that every decision to continue is a sunk-cost error. New information, future value, switching costs, or being close to useful completion can make continuation reasonable.
Evidence review
well-supported overall; strength varies by decision type and contextWhat the evidence supports
The sunk cost effect is a documented tendency for irrecoverable prior investments of money, time, or effort to influence later choices. A meta-analytic review found clear evidence for the effect overall, while also showing that its size and moderators differ between utilization decisions and progress decisions. The effect should not be used to label every choice to continue: future value, switching costs, uncertainty, and how close a project is to useful completion can all be relevant to a forward-looking decision.
How researchers describe the pattern
Classic experiments linked sunk-cost behavior to reluctance to appear wasteful, while later work has connected it to several decision processes rather than one universal mechanism. In project settings, sunk costs can interact with the perceived need to complete the work. That interaction helps explain why sunk costs are one possible antecedent of escalation of commitment rather than a complete explanation for every escalation case.
Practical interpretation
For a current choice, put irrecoverable past costs in a separate line and evaluate the remaining options using costs and benefits from today forward. Compare continuing with the best realistic alternative use of the remaining money, time, and attention. If completion itself creates future value, include that value explicitly instead of treating 'we are already close' as either automatically rational or automatically biased.
Reviewed sources
- The psychology of sunk cost field study and experiments · 1985 · DOI 10.1016/0749-5978(85)90049-4
- Looking forward and looking back: integrating completion and sunk-cost effects within an escalation-of-commitment progress decision experimental study · 2001 · DOI 10.1037/0021-9010.86.1.104
- On the sunk-cost effect in economic decision-making: a meta-analytic review meta-analysis · 2015 · DOI 10.1007/s40685-014-0014-8
Editorial review: 2026-08-18. Evidence status describes this entry, not every study ever published on the topic.