What Is the Sunk Cost Fallacy? Definition, Examples and How to Avoid It

You’ve sat through ninety minutes of a film you stopped enjoying after twenty. You keep paying for a gym membership you never use because cancelling feels like “wasting” the last six months of payments. You stay in a job, a relationship or a project long after it stopped making sense, because of everything you’ve already put in.

All three are examples of the sunk cost fallacy, one of the most common and most costly biases in everyday decision-making.

What is the sunk cost fallacy?

A sunk cost is any resource, time, money, effort, emotional investment, that has already been spent and cannot be recovered, no matter what you choose to do next. The sunk cost fallacy is the tendency to let those unrecoverable past costs influence a decision that should really be based only on future costs and benefits.

Early research on the phenomenon described it plainly: people show “a greater tendency to continue an endeavor once an investment in money, effort, or time has been made,” even when continuing no longer makes sense on its own terms. The mistake isn’t caring about the past. It’s letting something you can never get back decide something you still have full control over.

Why “cutting your losses” is actually the rational move

From a purely economic standpoint, a sunk cost should have zero influence on your next decision, because it exists in every option in front of you equally. The only thing that should matter is: given where I am right now, what choice makes the most sense going forward? Whether you spent $10 or $10,000 to get here doesn’t change what the next dollar will buy you.

This is deeply counterintuitive, because it feels wrong to “waste” what you’ve already put in. But the money, time or effort is already gone either way. The only real question is whether spending more is worth it from this point forward.

Real-world examples

Money and investing

Holding onto a falling stock because you’ve already lost money on it, rather than assessing it fresh: would you buy this stock today, at this price, given what you now know? A related pattern, called escalation of commitment, was documented in classic research on decision-making in organisations, showing that people and even entire companies often pour more resources into a failing course of action specifically because of what they’ve already invested, not despite it.

Relationships

Staying in an unfulfilling or unhealthy relationship because of the years already spent together, rather than asking honestly whether it’s the right relationship going forward. See signs of an emotionally unavailable person if you recognise a pattern of staying too long out of investment rather than genuine connection.

Careers and education

Continuing down a career path you no longer want because of years of training or a degree already completed, even when a change would leave you better off from here. The sunk cost is the years already spent; they don’t grow back if you stay unhappy for longer.

Everyday life

Finishing a bad meal because you already paid for it. Continuing a book you’re not enjoying because you’re “already halfway through.” Attending a boring or costly event because you already bought the ticket, when your actual evening would be better spent elsewhere.

Business

Companies have famously continued expensive projects, from stalled construction to failing product lines, well past the point where the numbers justified it, partly because of the scale of what was already spent. Research on the effect notes it can intensify with the size of the investment and public commitment to the decision, which is part of why large organisations are especially prone to it.

Why does the sunk cost fallacy happen?

• Loss aversion. Research in behavioural economics finds that losses generally feel more painful than equivalent gains feel good, so “admitting” a loss by quitting feels worse than continuing to hope it works out.
• Wanting to avoid feeling wasteful. Quitting can feel like an admission that the earlier investment was pointless, which is uncomfortable, even though the investment is equally “gone” either way.
• Consistency and identity. Once you’ve told others (or yourself) that you’re committed to something, reversing course can feel like admitting you were wrong, which threatens self-image.
• Confusing effort with value. We tend to assume that because something cost a lot, it must be worth continuing, when the two are often unrelated. See what is confirmation bias for how we then look for reasons to justify staying the course.

How to avoid the sunk cost fallacy

1. Ask the “fresh start” question

“Knowing everything I know now, if I were starting today, would I choose this?” If the honest answer is no, the fact that you’ve already invested doesn’t change that answer; it just makes it harder to admit.

2. Separate the decision from the emotion of “wasting” something

Try reframing: the time or money is already spent regardless of what you do next. The only real choice is what happens from here, and that choice deserves to be made on its own merits.

3. Get an outside view

Ask what you’d advise a friend to do in the exact same situation, with the exact same numbers, but without your personal attachment to the earlier investment. Outside perspectives are far less swayed by sunk costs than the person who made them.

4. Set decision checkpoints in advance

Before starting something significant, decide in advance what conditions would mean “stop”: “If costs exceed X, or if this isn’t working by [date], I’ll reassess with fresh eyes.” Deciding this before you’re emotionally invested makes the later decision much easier.

5. Track future costs and benefits only

When weighing whether to continue, write down only what still lies ahead: What will it cost from here? What will you gain from here? Leave the historical total out of the calculation entirely; it’s the same regardless of your choice.

6. Watch for public commitment pressure

If you’ve told others about your plan, notice whether that’s making it harder to reconsider. It’s fine to change course quietly and thoughtfully; you don’t owe anyone a justification for updating a decision with better information.

A worked example

Priya has spent eight months and a significant amount of savings building an app that isn’t gaining users.

• Sunk cost thinking: “I’ve put in so much already, I can’t quit now.”
• Fresh-start question: “If I had today’s information and hadn’t spent anything yet, would I start this project?” Honestly, no.
• Future-only view: she asks what continuing for another six months will cost, and what it’s actually likely to gain, based on current traction, not hope.
• Outside view: a mentor, uninvested in the eight months already spent, suggests she’d have better odds pivoting the idea or moving on.
• Decision: she stops the project, keeps the skills and lessons, and redirects her effort, without treating the eight months as wasted, since they taught her something real.

It also connects to the halo effect: once we’ve committed to something, we tend to see it more favourably than the facts support.

Common mistakes

• Confusing “cutting losses” with “giving up too easily”. The fallacy is about ignoring current evidence in favour of past investment, not about never persisting through hard times. Genuine perseverance is based on future potential, not sunk costs.
• Letting public commitments override private judgement. Changing your mind with new information is a sign of good thinking, not weakness.
• Applying the concept as an excuse to quit everything difficult. The test is the fresh-start question, not simply “this feels hard now.”
• Ignoring emotional sunk costs. Time and money are the classic examples, but emotional investment (in a relationship, an identity, a decision you defended publicly) works the same way and is just as worth checking.

Frequently asked questions

What is a simple example of the sunk cost fallacy?

Finishing a meal you don’t enjoy because you already paid for it, even though eating more brings no benefit and the money is spent either way.

Is the sunk cost fallacy the same as being persistent?

No. Persistence is choosing to continue because the future prospects genuinely justify it. The sunk cost fallacy is continuing mainly because of what you’ve already spent, regardless of future prospects.

How do you overcome the sunk cost fallacy?

Ask whether you’d start the same thing today with no prior investment, focus only on future costs and benefits, and get an outside opinion from someone without your emotional stake in the past investment.

Does the sunk cost fallacy apply to relationships?

Yes. Staying in a relationship mainly because of years already invested, rather than the relationship’s actual current and future value, is a common form of the fallacy.

Why do businesses fall for the sunk cost fallacy so often?

Larger, more public investments create more pressure to justify continuing, and more people whose reputations are tied to the decision, both of which intensify the effect.

Is it ever rational to consider past investment?

Only indirectly, for instance if past investment created skills, relationships or assets that genuinely improve your future options. The past spending itself, though, should not be the reason to continue.

The bottom line

What you’ve already spent is gone whether you continue or stop, so it should have no weight in deciding what to do next. When you notice yourself thinking “I can’t quit now, I’ve put in too much,” ask instead: knowing what I know today, would I choose this again? Let that answer, not the past, decide.