How Does the Sunk Cost Fallacy Appear in Investing?
An investor who bought a stock at $100 watches it fall to $40. Rather than objectively evaluating whether the stock will recover, they hold on because they have "too much invested to sell now." The $60 loss is a sunk cost — it is gone regardless of what happens next. The rational question is: "Would I buy this stock today at $40 given everything I know?" If not, holding is just as irrational as buying would be.
Where Else Does It Show Up in Personal Finance?
The sunk cost fallacy drives many financial mistakes: keeping an expensive car because you already spent $5,000 on repairs, staying in a bad subscription because you paid for the annual plan, finishing a degree program you dislike because you already completed two years, or continuing to pour money into a failing business. In each case, past spending should not dictate future decisions.
How Do You Avoid the Sunk Cost Fallacy?
Ask yourself: "If I were starting from scratch today, would I make this same choice?" If not, the sunk cost is influencing your judgment. Set predetermined exit criteria for investments before you buy. Conduct regular portfolio reviews focused on forward-looking merit, not historical cost. Accept that cutting losses is often the most profitable long-term decision, even though it feels like admitting failure.
Frequently asked questions
Is it always wrong to consider sunk costs?
From a purely rational economic standpoint, yes — sunk costs should be irrelevant to future decisions. In practice, there can be reputational or emotional factors worth weighing. But for most financial decisions, ignoring sunk costs leads to better outcomes.
How does the sunk cost fallacy relate to loss aversion?
Loss aversion makes the pain of realizing a loss feel twice as powerful as an equivalent gain. This amplifies the sunk cost fallacy because selling at a loss triggers that pain, causing people to hold losing positions irrationally to avoid the emotional experience of acknowledging the loss.