The Sunk Cost Fallacy in Investing
Refusing to sell a loser 'until it comes back to what I paid' is the sunk cost fallacy in action. Your purchase price is irrelevant to whether the investment is worth holding now.
Don't have time? Here's what you need to know:
- 1The sunk cost fallacy is holding a loser because of what you paid; the market has no memory of your purchase price.
- 2The rational test is forward-looking: if you wouldn't buy the position today at its current price, you have no reason to hold it.
- 3In taxable accounts, selling a loser can save money via tax-loss harvesting — the position may be worth more sold than held.
- 4Broad index funds sidestep the trap by handling turnover internally, so no single stock becomes an emotional anchor.
Throwing Good Money After Bad
The sunk cost fallacy is the tendency to keep committing to something because of what you've already invested, rather than judging it on its future merits. In everyday life it is finishing a bad movie because you paid for the ticket, or staying in a project because you've already sunk months into it. The money or time already spent is gone either way — but it irrationally pulls you toward throwing more after it.
In investing, the fallacy has a specific and costly shape: holding a losing position purely because of the price you paid, waiting for it to 'come back to even' before you'll sell. The market has no memory of your purchase price and no obligation to return to it. A stock that fell 50% does not owe you a recovery — it simply needs to be a good investment from here, or it doesn't.
Why Your Purchase Price Doesn't Matter
The only rational question about any holding is forward-looking: given everything you know today, is this the best place for that money going forward? What you originally paid is a sunk cost — historical and unchangeable — and it should carry zero weight in that decision. Anchoring to your purchase price is a classic mental accounting error that keeps capital trapped in poor investments.
A useful test cuts straight through the fallacy: if you did not already own this position, would you buy it today at the current price? If the honest answer is no, then continuing to hold it is the same mistake as buying it fresh — you're just hiding the decision behind what you paid. The 'break-even' you're waiting for is a number that exists only in your head, not in the market.
Tip: Run the 'would I buy it today?' test on any position you're reluctant to sell. If you wouldn't buy it now at today's price, you have no rational reason to keep holding it.
The Tax Twist Most People Miss
There is a financial cruelty to the sunk cost fallacy in taxable accounts: selling a loser can actually save you money. Tax-loss harvesting lets you realize a capital loss and use it to offset capital gains elsewhere, and in many systems to offset a limited amount of ordinary income too. The very position you're clinging to in hopes of breaking even may be worth more to you sold than held.
This flips the usual emotional logic. Instead of a painful admission of failure, selling a losing investment can be a deliberate tax move that puts cash back in your pocket while you redeploy the proceeds into something better. The table contrasts the fallacy-driven instinct with the rational play.
| Situation | Sunk-cost instinct | Rational approach |
|---|---|---|
| Position down 40% | Hold until it returns to break-even | Ask: would I buy this today? |
| Better opportunity exists | Stay put to avoid 'locking in' the loss | Move capital to the better investment |
| Taxable account | Avoid selling at a loss | Harvest the loss to offset gains/income |
| A single stock cratered | Wait and hope for recovery | Reassess on fundamentals, not your cost |
How Broad Index Investing Sidesteps It
The sunk cost fallacy is most dangerous with individual stocks and concentrated bets, where a single position can fall and become an emotional anchor you refuse to abandon. Broad index investing structurally reduces this trap. When you own thousands of companies through a fund like VTI, no single failing company becomes a personal grudge match — the index quietly drops the losers and lets the winners grow without any decision from you.
This is one of the underrated behavioral benefits of indexing: it removes most of the wrenching sell-or-hold decisions that activate the fallacy. You are not married to any one stock's purchase price, because the fund handles turnover internally. For the broad market itself, the right response to a decline is usually to keep buying through it, not to agonize over a break-even point that doesn't apply to a diversified portfolio.
Important: Don't confuse a diversified index fund with a single beaten-down stock. Riding the broad market through a downturn is sound; clinging to one collapsing company to avoid admitting a loss is the sunk cost fallacy.
Frequently Asked Questions
How do I know if I'm holding a loser due to the sunk cost fallacy?
Ask yourself one question: 'If I had this money in cash today, would I buy this exact position at its current price?' If the answer is no but you're holding anyway because you don't want to realize the loss or want to wait for break-even, that's the sunk cost fallacy. The purchase price is shaping a decision it shouldn't touch.
Isn't selling at a loss just locking in the loss?
The loss already exists the moment the price falls — selling only makes it official on paper. Whether you hold or sell, your current wealth is the same. The real question is whether the money would grow better elsewhere from here. If it would, holding on doesn't undo the loss; it just keeps the capital underperforming.
Does the sunk cost fallacy apply to dollar-cost averaging into a down market?
No — that's a different and often sound behavior. Continuing to buy a broad, diversified fund as it falls means buying more shares at lower prices, which has historically helped long-term returns. The fallacy is specifically about clinging to a poor individual position because of what you paid, not about steadily investing in the whole market.
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Alex Harrington
CFA Level II Candidate, Finance & Economics
Alex Harrington is an independent ETF researcher and personal finance writer with over 8 years of experience analyzing exchange-traded funds. A CFA Level II candidate with a background in economics, Alex has reviewed 800+ ETFs and helped thousands of beginners build their first investment portfolios through clear, jargon-free education.
This content is for educational purposes only and does not constitute financial advice. Past performance does not guarantee future results. Consult a licensed financial advisor before making investment decisions.