Picture this: a company has poured years of work and tens of millions of dollars into a product line that clearly isn’t working. The data says stop. The market says stop. Yet the board keeps approving new budgets. Why? Because walking away now would feel like admitting the whole thing was a mistake. The sunk cost fallacy is a cognitive bias that leads us to continue investing in something because of what we’ve already invested, even when the current costs outweigh the benefits. It’s one of the most stubbornly human quirks in all of decision-making, and it plays out everywhere, from boardrooms to relationships to the half-eaten meal you force yourself to finish. Understanding it isn’t just intellectually interesting. It can change the quality of every significant decision you make.
What the Sunk Cost Fallacy Actually Is
The sunk cost fallacy is our tendency to follow through with something that we’ve already invested heavily in, be it time, money, effort, or emotional energy, even when giving up is clearly a better idea. The term itself comes from economics, where a “sunk cost” is a past expense that simply cannot be recovered.
Sunk costs refer to costs that have already been incurred and cannot be recovered, including time, money, resources, and other investments. These costs should not influence current decision making because they are irretrievable. The logic is airtight. The problem is that human psychology rarely follows airtight logic.
Rational decision-making looks only at future costs and future benefits. The sunk cost fallacy is what happens when past losses hold future decisions hostage. That gap between what we should do and what we actually do is exactly where the fallacy lives.
The Concorde: A Billion-Dollar Blueprint for the Bias
In January 1976, the supersonic Concorde jet went wheels-up for its first commercial flight after an investment of $2.8 billion from the British and French governments. Even when it became clear that the plane wasn’t profitable, investors continued to pour money into the failing project for another 27 years. This incident gave birth to the term “Concorde fallacy,” which describes how people continue with failing endeavors because they’ve already invested so much.
The British government privately regarded the project as a commercial disaster that should never have been started. Political and legal issues made it impossible for either government to pull out. That combination of public accountability and prior commitment is a particularly toxic mix.
The Concorde became the textbook case, but it was far from the last. History has repeated this story in government infrastructure, corporate strategy, and personal careers more times than anyone cares to count.
How the Brain Gets Trapped: The Neuroscience Behind the Bias
Research published in Brain Research found that higher sunk costs increased activity in lateral frontal and parietal cortices involved in risk-taking behavior, while lower incremental costs activated reward-sensitive regions including the striatum. Critically, no overlapping brain areas responded to both sunk cost and incremental cost, suggesting these are processed by entirely different neural systems.
This helps explain why simply knowing that sunk costs should be ignored does not eliminate their influence. They activate separate circuits from those evaluating future prospects. Knowing about the bias and being immune to it are two very different things.
A 2024 Oxford study combining neuroimaging with lesion studies found that patients with damage to key sunk-cost-processing regions were more flexible about switching to better goals. This suggests the sunk cost bias may serve an adaptive function in maintaining goal persistence, but it just overgeneralizes to situations where abandonment is the rational choice.
The Psychology Underneath: Loss Aversion and the Fear of Waste
The sunk cost fallacy is driven by loss aversion, the well-documented asymmetry in how humans experience losses and gains identified by Kahneman and Tversky in their work on prospect theory. Stopping a failing project does not just mean accepting a future without that project’s returns, it means converting an uncertain loss into a confirmed one. The mind treats the unrecoverable investment as still potentially retrievable if you just persist long enough, because stopping makes the loss final and undeniable.
Sunk cost appears to operate chiefly in those who feel a personal responsibility for the investments that are to be viewed as a sunk cost. The more your identity is wrapped up in a decision, the harder it becomes to reverse it.
Sunk costs are particularly powerful when the investment is tied to identity or public commitment. A founder who has spent five years building a company is not just weighing financial returns. They are weighing what stopping says about them, about their judgment, about the years of their life they devoted to the venture.
Corporate Giants and the Cost of Holding On Too Long
Meta’s recent metaverse losses provide a contemporary example still in progress. Since rebranding from Facebook in October 2021, the company’s Reality Labs division has lost an estimated $70 to $77 billion cumulatively, approximately $1 billion per month since June 2022.
In December 2024, Meta announced roughly a third of budget cuts to Reality Labs and a pivot to artificial intelligence. The stock jumped over four percent on news of the metaverse pullback. The market, apparently, had been waiting a long time for that decision.
The sunk cost fallacy costs organizations billions of dollars annually and destroys countless careers. This cognitive bias leads to irrational decisions that explain why the majority of mergers fail and why companies like Kodak, Nokia, and Blockbuster continued investing in dying business models while more agile competitors captured their markets.
The Mergers and Acquisitions Trap
Mergers and acquisitions represent among the highest-stakes decisions executives make and among the most susceptible to sunk cost contamination. McKinsey and Company reports that roughly seven out of ten mergers fail to achieve expected synergies. Harvard Business School studies put failure rates at a similar range.
KPMG research of 700 mergers found the vast majority were unsuccessful in creating shareholder value. McKinsey’s analysis showed more than half of acquisition programs did not earn back their cost of capital. The pattern is extraordinarily consistent across decades of data.
Wharton finance professor Marius Guenzel presented evidence that firms “systematically fail to ignore sunk costs and that this leads to significant distortions in investment decisions.” CEOs tend to ignore the standard economic maxim that sunk costs shouldn’t matter when they make acquisitions, and he noted that it is very much a human trait.
IT Projects and Infrastructure: Where Escalation Becomes Institutional
Nowhere does the sunk cost fallacy inflict more damage than in large-scale projects where massive upfront investments create enormous psychological pressure to continue regardless of evidence. The Standish Group’s CHAOS reports have documented IT project failure rates for three decades, consistently finding that the majority of technology initiatives fail to deliver promised value.
Projects averaged nearly twice the original cost estimates. Large companies fared worst, with only a small fraction of large company projects succeeding and those delivering far fewer features than originally promised.
Swedish research published in ScienceDirect in 2024 found that cost escalation during planning stages is substantial and highly skewed, with a “long right tail” of catastrophic overruns. More troubling, project decisions are “effectively locked in before projects’ costs and benefits have been thoroughly assessed,” representing institutionalized escalation of commitment.
Sunk Costs in Personal Life and Relationships
People can remain in failing relationships because they “have already invested too much to leave.” This version of the bias is often the most emotionally costly, and the hardest to name clearly when you’re inside it.
In education, students may persist in their choices of schools, majors, or academic programs even after realizing these decisions might be suboptimal, in order to avoid the psychological discomfort or sense of loss associated with abandoning prior investments. Due to the continuity of educational paths and the irreversibility of resources already invested, these prior commitments often become a significant psychological driver for maintaining the current trajectory.
The danger of the sunk cost fallacy is that getting hung up on the past can pointlessly incur new, future costs. It can lead to making irrational career decisions, and can end up meaning letting your future self suffer to please your past self.
Can We Learn to Be Less Susceptible?
Research published in early 2025 found that students become nearly fifteen percent less susceptible to the sunk cost fallacy after learning about it. Students who had taken economics previously also exhibited lower susceptibility in all time periods. This is actually encouraging news. Awareness measurably moves the needle.
Multiple studies have established that older adults are less susceptible to the sunk cost fallacy than younger adults. Older adults focus less on negative information generally, a phenomenon called the “positivity bias,” and may also have accumulated more experience recognizing sunk cost situations.
General cognitive ability does not appear to reduce susceptibility. Research found that raw intelligence fails to protect against the sunk cost trap. Being smart, in other words, is not the same as being immune. Experience and deliberate reflection seem to matter more.
How to Actually Break Free: Practical Strategies That Work
Before beginning any significant investment, define in advance the conditions under which you would exit. What performance level, after what time period, would lead you to stop? Writing these criteria down before the investment begins, when sunk cost reasoning has not yet taken hold, creates a pre-committed standard against which future continuation can be objectively measured.
Regularly asking yourself “Knowing what I know now, would I start this project or relationship or activity again today?” can help. If the answer is no, it might be time to cut your losses. This mental reset helps eliminate the psychological weight of past investments.
At significant budget overruns or milestone delays, an external reviewer is not a luxury but a necessity. People inside a project are inherently biased. They have invested in it and feel the sunk cost most acutely. Someone with no sunk costs in the project can ask the question “should we stop?” without the emotional weight.
One useful method is to acknowledge the costs of staying on course and follow up with a blank-slate inquiry: given the facts at hand, what would you decide if you’d never made a particular investment to begin with?
Conclusion: Folding Is Not Failing
Redefining stopping as a leadership competency may be the most important cultural shift available to organizations. The fear of accountability is partly so powerful because stopping a project is often interpreted as failure. The most effective leaders are the ones who stop quickly and clearly when something is not working. If an organization explicitly signals that failing fast is smart and failing slow is expensive, it changes the social norm around stopping.
In reality, admitting failure early is often viewed by senior leaders and employees as a mark of maturity. It shows you’re willing to put the organisation first rather than your own ego.
The cards you’ve already played are gone regardless of what you do next. The only real question is whether the next card you put down gives you a better hand or a worse one. Knowing the difference, and acting on it clearly, is one of the most underrated skills in both life and business.
