The sunk cost fallacy is the tendency to keep investing time, money, or effort in something because of what you have already put in, rather than because it is still the best choice going forward. Past costs cannot be recovered whatever you decide, so a clear decision looks only at future costs and benefits; the fallacy is letting the unrecoverable past make that decision for you.
Almost everyone falls into it. You sit through a dull film because you paid for the ticket, stay in a course you no longer want because you are halfway through, or keep repairing a car that has become a money pit. This guide explains what the sunk cost fallacy is, why the mind is so drawn to it, what the research shows, and a practical set of questions that help you decide when to persist and when to walk away.
What Is a Sunk Cost?
In economics, a sunk cost is a cost that has already been incurred and cannot be recovered. The money you spent on a non-refundable concert ticket is sunk. So are the three years you spent training for a career, or the hours you put into a project at work. Whatever you decide next, that investment stays spent.
Standard decision theory says sunk costs should be irrelevant to future choices. The only question that matters is: from this point on, which option gives the best result? If the concert is going to be miserable because you are sick, the rational move is to stay home, because going will not get your money back. It will only add a bad evening to the loss.
The fallacy happens when we treat what we have already spent as a reason to keep spending. The economist Richard Thaler described this pattern in a 1980 paper on consumer choice, noting that people often behave as if paying for something obliges them to use it, even when using it makes them worse off.
Everyday Examples of the Sunk Cost Fallacy
- The gym membership. You keep paying for a membership you rarely use because canceling would feel like admitting the money was wasted.
- The unfinished book. You force yourself through a book you dislike because you are already two hundred pages in.
- The buffet. You eat past the point of comfort because you paid a fixed price and want to "get your money's worth."
- The degree or career. You continue down a path that no longer fits because of the years and tuition already invested.
- The relationship. You stay in a relationship that has been unhappy for a long time partly because of how many years you have spent together.
- The work project. A team keeps funding a failing initiative because cancelling it would make the previous budget look wasted.
- The investment. You hold a falling stock waiting to "break even," rather than asking whether you would buy it today at its current price.
Notice that in each case, the past investment is real and the feelings about it are understandable. The mistake is not caring about the past. It is letting the past answer a question about the future.
What the Research Shows
The theater ticket study
The classic demonstration comes from Hal Arkes and Catherine Blumer, published in 1985. In one of their studies, people buying season tickets to a university theater series were randomly given either the full price, a small discount, or a larger discount. Those who paid full price attended more plays during the first half of the season than those who received discounts. Nothing about the plays differed; the only difference was how much people had paid. Having spent more made them feel more obligated to attend.
Arkes and Blumer also used a now-famous hypothetical: imagine you have paid for a weekend ski trip to Michigan and later buy a cheaper ticket for a trip to Wisconsin that you expect to enjoy more. Then you realize both trips are on the same weekend and neither ticket can be refunded. Which do you go on? Many participants chose the more expensive Michigan trip, even though they expected to enjoy Wisconsin more. The money was gone either way, yet the larger sunk cost pulled harder.
Escalation of commitment
In organizations, the same pattern is often called escalation of commitment. Barry Staw's 1976 paper "Knee-Deep in the Big Muddy" found that people who were personally responsible for an initial investment decision that went badly tended to allocate more money to that same course of action than people who had not made the original choice. Admitting the first decision was a mistake felt costly, so they doubled down.
The Concorde fallacy
Biologists Richard Dawkins and Tamsin Carlisle used the phrase "Concorde fallacy" in 1976, referring to the British and French governments' continued funding of the Concorde supersonic jet after it was widely seen as unlikely to be commercially viable. The name stuck as a shorthand for continuing a project mainly because so much has already been sunk into it.
Who is more prone to it?
In a 1999 review, Hal Arkes and Peter Ayton noted that clear evidence of sunk cost behavior in non-human animals was hard to find, and that young children seemed less prone to it than adults in some studies. One interpretation is that the fallacy grows out of a learned adult rule, such as "do not waste," being applied too broadly. Research by JoNell Strough and colleagues, published in 2008, found that older adults were less likely than younger adults to commit the sunk cost fallacy in their tasks, suggesting that life experience may help some people let go of past costs.
There is also some encouraging evidence that the habit can be trained. Richard Larrick, James Morgan, and Richard Nisbett reported in 1990 that teaching people cost-benefit reasoning principles was associated with better decisions on problems involving sunk costs. Knowing about the fallacy does not make you immune, but it helps.
Why the Sunk Cost Fallacy Feels So Convincing
If the logic is so simple, why is the fallacy so hard to resist? Several forces work together:
- Loss aversion. Daniel Kahneman and Amos Tversky's prospect theory (1979) showed that losses feel more painful than equivalent gains feel good. Walking away makes the loss feel final, while continuing keeps the hope of recovery alive. This is closely connected to negativity bias, the broader tendency for bad outcomes to weigh more heavily than good ones.
- Not wanting to waste. Most of us were taught that waste is wrong. That is a good value, but it misfires when continuing actually wastes more: more time, money, or energy on something that will not pay off.
- Protecting self-image. Quitting can feel like admitting you were wrong. As Staw's work suggests, the more personally responsible you feel for the original decision, the harder it is to reverse.
- Social pressure. Other people know what you invested, and you may worry about how quitting will look. In reality, people tend to think about your choices far less than you imagine, a pattern known as the spotlight effect.
- Status quo bias. William Samuelson and Richard Zeckhauser described in 1988 how people disproportionately stick with the current option. Continuing requires no new decision; stopping does.
Sunk Cost Fallacy vs Healthy Perseverance
Here is the important nuance: not every decision to keep going is a fallacy. Persistence is how difficult and worthwhile things get done. Learning an instrument, building a business, recovering from injury, and repairing a relationship all involve stretches where progress is slow and quitting is tempting.
The difference lies in the reason. Perseverance is continuing because the future payoff still justifies the future cost. The sunk cost fallacy is continuing because of what you have already spent, even when the future payoff no longer justifies it. Two people can make the same choice to keep going, one wisely and one not, depending on why.
A growth mindset helps here in two directions. It encourages you to persist through difficulty when growth is genuinely possible, and it also frees you to quit without treating it as a verdict on your worth. Changing course in light of new information is a skill, not a failure.
How to Stop Falling for the Sunk Cost Fallacy
1. Ask the "clean slate" question
The most useful single question is: "If I had not already invested anything, would I choose this today?" If you were offered this job, this project, this stock, or this commitment fresh, starting today, with what you now know, would you say yes? If the honest answer is no, past investment is likely doing the deciding.
2. Separate the past from the future on paper
Draw two columns. In the first, write everything you have already spent: money, years, effort, emotion. Acknowledge it fully. Then draw a line under it and accept that none of it changes based on your next move. In the second column, write only the future costs and benefits of each option. Make the decision using the second column alone.
3. Reframe what you have spent
Past investment is rarely pure waste. The years in a career you are leaving gave you skills, contacts, and self-knowledge. The money spent on an abandoned project taught you something about what does not work. Naming what you gained makes letting go feel less like losing everything.
4. Set exit criteria in advance
Before you start something new, decide what would make you stop: a budget limit, a deadline, or a specific result you need to see by a certain date. It is much easier to make this judgment calmly at the beginning than in the middle, when commitment and pride are already involved. Psychologist Gary Klein's "pre-mortem" technique fits well here: imagine the project has failed a year from now and ask what went wrong. The answers often point to warning signs worth watching for.
5. Get an outside view
Ask someone who has no investment in the decision what they would do. A friend, mentor, or colleague who did not make the original choice is not anchored by its costs and can often see the situation more plainly. Staw's research suggests that people who did not make the initial decision are less prone to escalate.
6. Calculate the cost of continuing
We often frame quitting as the costly option. Flip it: what will continuing cost over the next six months or year in time, money, energy, and missed opportunities? Every hour spent on something that is not working is an hour unavailable for something that might. A tool like the Eisenhower Matrix can help you see whether this commitment still deserves a place among your priorities.
7. Check it against your values
Sometimes the best guide is not a spreadsheet but your core values. Does continuing reflect what matters most to you now, or what mattered to the person who started it? People change, and commitments made by an earlier version of you deserve to be reviewed. Our guide on how to find your core values and live by them offers a simple process for clarifying them.
A Reflection Exercise for a Decision You Are Stuck On
If something in your life feels heavy and you are not sure whether to keep going, set aside twenty minutes and write answers to these prompts:
- What have I already invested here? List it all without judgment.
- What have I gained from that investment, even if things have not worked out as planned?
- If I were starting fresh today, would I choose this? Why or why not?
- What would continuing cost me over the next year? What would stopping cost me?
- What am I afraid people will think if I stop? How much does that really matter?
- What would I tell a close friend in exactly this situation?
- What is one small step I could take this week to test either option?
You do not need to reach a final decision in one session. Often the writing itself shows you that you have been thinking in circles, and that the real question has been answered for a while. If you notice the same worries repeating, our guide on how to stop overthinking can help you break the loop.
Letting Go Without Regret
Walking away from a significant investment can bring grief, even when it is the right choice. That is normal. You are not just leaving a project or a plan; you are releasing a future you had imagined. Give yourself room to feel that. It also helps to avoid measuring your choice against what others appear to be doing. Seeing someone else succeed at the thing you abandoned can trigger second-guessing, which is why learning to stop comparing yourself is so useful during a transition.
The aim is not to become someone who quits at the first sign of difficulty. It is to become someone who chooses with open eyes, who stays because the future is worth it, and who leaves when it is not, without being held hostage by what has already been spent.
Frequently Asked Questions
What is the sunk cost fallacy in simple terms?
The sunk cost fallacy is continuing with something because of what you have already invested in it, rather than because it is still the best choice. Since past costs cannot be recovered, they should not decide what you do next. Only future costs and benefits should.
What is an example of the sunk cost fallacy?
A common example is staying at a boring movie because you paid for the ticket. The money is gone whether you stay or leave, so staying only adds a wasted evening. Other examples include keeping an unused gym membership or holding a failing investment to break even.
Why do people fall for the sunk cost fallacy?
Several forces combine: loss aversion makes walking away feel like locking in a loss, people dislike waste, and quitting can feel like admitting a mistake. Social pressure and a general preference for the status quo add to the pull.
Is it always wrong to keep going after a big investment?
No. Continuing is wise when the future benefits still outweigh the future costs. The fallacy only applies when past investment is the main reason you keep going. Persistence and the sunk cost fallacy can look the same from outside; the difference is the reason behind the choice.
How do I avoid the sunk cost fallacy?
Ask yourself whether you would choose the same option today if you had invested nothing so far. Set exit criteria before starting new commitments, get an outside opinion from someone uninvolved, and compare only the future costs and benefits of each option.
What is the difference between sunk cost fallacy and escalation of commitment?
They are closely related. The sunk cost fallacy describes the individual reasoning error, while escalation of commitment is the term often used in organizational research for continuing to invest in a failing course of action, especially by the people who made the original decision.
