The Sunk Cost Fallacy in Investing: Why Most Investors Hold Losers Too Long

In 1985, the Concorde supersonic jet project continued to receive funding for years despite mounting evidence it was commercially unviable. When British and French governments finally cancelled it, the official reason given was that so much had already been spent that stopping would be 'wasting the investment' — a classic example of the sunk cost fallacy.

Investors make the same mistake — frequently and at significant financial cost. You hold a falling stock because 'I'm already down 30%, I can't sell now.' You keep averaging into a wrong investment thesis because 'I've already put in so much.' You stay in a bad relationship with your advisor because 'we've been working together for 10 years.'

This article examines the sunk cost fallacy in investment decision-making, provides psychological and economic frameworks for understanding it, and gives practical tools for breaking free from it.

What Is the Sunk Cost Fallacy?

The sunk cost fallacy is the cognitive bias of continuing a behavior or endeavor because of previously invested resources (time, money, or effort), even when the current evidence suggests stopping or pivoting would produce better outcomes.

The key word is 'sunk': a cost is 'sunk' if it cannot be recovered. Your ₹3 lakh invested in a stock that is now worth ₹1.5 lakh — the ₹1.5 lakh loss is already gone. The only relevant question now is: given current information, should you hold, sell, or average down?

The irrational investor asks: 'How much have I already lost?' The rational investor asks: 'What is the expected outcome from here?'

Callout::info Your past investment should not influence your present decision. Only current and future prospects should. A cost that cannot be recovered should be treated as irrelevant to forward-looking decisions.

How Sunk Costs Manifest in Investing

1. The Stockholder's Dilemma

Imagine you bought 1000 shares of a mid-cap IT company at ₹800 per share — a ₹8 lakh investment in 2023. Today the stock trades at ₹480. Your unrealized loss is ₹3.2 lakh, or 40% of your investment. You have been reading about recovery but the company's fundamentals are deteriorating.

Many investors in this situation: - Hold indefinitely because selling 'locks in' the loss (it doesn't — it recognizes it) - Average down because the stock is 'so cheap' — without independent analysis of whether ₹480 is truly a bargain - Hope-based investing — substituting hope for analysis

2. The Mutual Fund SIP Trap

Investors continue SIPs in underperforming funds for months or years because 'I've already paid so many installments.' The logical question should be: is this fund likely to deliver better risk-adjusted returns going forward relative to its category benchmark and peers? If the answer is no, stopping the SIP and redirecting to a better fund is the correct, rational action.

3. The Advisory Relationship Hangover

You have worked with the same financial advisor for 15 years. The advisor's returns have been consistently 3–4% below comparable benchmarks after fees for the last 5 years. But you stay because 'switching advisors costs effort.' The right question is: who is likely to serve my wealth better over the next 15 years?

The Psychology: Why We Fall For It

Loss Aversion

Prospect Theory, developed by Daniel Kahneman and Amos Tversky in 1979, established that losses hurt roughly twice as much as equivalent gains feel good. This means investors will incur significant additional losses to avoid crystallizing a small percentage loss — a tragedy of bias-driven decision-making.

Ego and Self-Justification

Admitting an investment was wrong feels like admitting a personal failure. This emotional weight creates a powerful resistance to selling. Behavioral economists call this 'self-justification bias' — the tendency to double down on a decision once made.

Commitment and Consistency Principle

Once we have committed to a course of action — taken a position, made an investment, engaged an advisor — we feel psychological pressure to remain consistent with that commitment. The consistency impulse becomes an investor's liability when it prevents necessary course corrections.

What the Data Actually Shows

A Practical Framework for Decision-Making

The Forward-Looking Test

Before making any investment decision, ask: 'If I had ₹X in cash today and had never invested in this before, would I invest that amount in this stock/mutual fund/position today?' If the answer is no, your past investment is irrelevant — the rational decision is whatever is right going forward.

The Zero-Based Portfolio Review

Every 6 months, approach your portfolio as if starting from zero. For each holding, ask: 'Knowing what I know now, would I enter this position at the current price?' If no, it is a candidate for a change.

The Regret Minimization Criterion

Would you regret selling more than you would regret holding? Investors who applied this frame were significantly more likely to make effective portfolio changes, according to University of Michigan research.

Actionable Steps to Overcome Sunk Cost Bias

1. Decouple decisions from entry price. Write the current price, your original price, and the decision you would make with NO prior position. The contrast will be revealing. 2. Set trailing stop-losses based on fundamentals, not percentages. A 15% trailing stop based on deteriorating fundamentals is more rational than a 30% price-anticipate stop. 3. Reduce portfolio check frequency. Investors who check daily show higher sunk cost bias than those who review quarterly. 4. Maintain a Decision Journal. Every time you hold a losing position, write the reason you are NOT selling. If the space is blank, you have identified your bias. 5. Seek independent verification. Show your holding to an advisor who has no connection to your original investment decision. Fresh eyes have no sunk costs.

Sources

1. Shefrin & Statman (1985) – The Disposition to Sell Winners Too Early and Ride Losers Too Long — Accessed June 3, 2026 2. Odean, T. (1998) – Are Investors Reluctant to Realize Their Losses? — Accessed June 3, 2026 3. Dalbar – Investor Behavior Study XXVIII (2024) — Accessed June 3, 2026 4. Kahneman & Tversky (1979) – Prospect Theory — Accessed June 3, 2026