Psychology
The Sunk Cost Fallacy: Why We Persist with Losses
Quick fact
The term 'sunk cost' comes from economics, but the fallacy is so strong that people will even continue eating a meal they dislike just because they paid for it, ignoring that the money is gone regardless.
Why this is interesting
You’ve already paid for the movie ticket, but the film is terrible. Do you stay to get your money’s worth? If you say yes, you’re falling for one of the most common traps in human thinking.
Read the full explanation
Understanding The Sunk Cost Fallacy: Why We Persist with Losses
Imagine you buy a non-refundable concert ticket for $100. On the day of the show, you feel tired and would rather stay home. But you think, 'I already spent $100, so I have to go.' The $100 is a sunk cost—it’s already spent and cannot be recovered. The rational decision should be based only on the future: will going to the concert bring you more enjoyment than staying home? If not, you should stay home, even though you’re losing the $100. The fallacy occurs because we let past investments influence decisions about the future. Our brains treat the loss of $100 as something we can 'avoid' by going to the concert, but the $100 is gone no matter what you do. This bias shows up everywhere: finishing a boring book because you’re halfway through, sticking with a career you hate because you’ve invested years in it, or waiting for a bus for 30 minutes because you don't want to 'waste' the wait.
A deeper explanation
The sunk cost fallacy arises from a combination of loss aversion and our desire to avoid admitting failure. Loss aversion, a key idea in behavioral economics, means we feel losses more intensely than equivalent gains. Giving up on something we’ve invested in feels like a loss—a waste of what we put in. We also have a strong need for consistency and self-justification: abandoning a project implies that our earlier decision was wrong, which threatens our self-image. So we 'throw good money after bad'—continuing to invest time, money, or effort into something that is unlikely to succeed. The mechanism is a misapplication of the 'commitment' principle, where we confuse past investment with future value. In reality, only future costs and benefits should matter. Recognizing this bias allows us to cut our losses and make decisions based on what will happen next, not what has already happened.