Investors tend to sell the stocks that have gone up and keep the ones that have gone down — precisely backwards from what works. Shefrin and Statman named this the disposition effect in 1985, and Odean confirmed it in real brokerage data. It is loss aversion and anchoring working together on the sell decision.
The old trading maxim is “cut your losses and let your winners run.” The disposition effect makes you do the reverse: you clip your winners (selling to lock in the good feeling of a gain) and ride your losers (holding to avoid the bad feeling of a loss). Over time this quietly fills a portfolio with the weakest positions while cashing out the strongest ones too soon — a slow, self-inflicted drag on returns.
The disposition effect isn’t new machinery — it is the loss aversion and anchoring from earlier in this path, combined. Loss aversion makes closing a loser feel unbearable, so you hold it. Anchoring on your purchase price makes a winner feel “done” the moment it is comfortably above what you paid, so you sell it. Put them together and you get exactly the wrong selling behavior.
Example (illustrative): you hold two stocks. One is up 25% with its reasons still intact; the other is down 20% because its outlook genuinely deteriorated. The disposition effect tells you to sell the winner (“take the profit”) and keep the loser (“wait for it to come back”) — the exact opposite of what the facts support.
This lesson is general investor education, not personalized investment advice. The +25% / -20% figures are illustrative arithmetic to show the pattern, not a prediction or a recommendation about any real stock.
It’s the well-documented tendency, named by Shefrin and Statman in 1985 and confirmed in real trading data by Odean, to sell investments that have gained and hold onto ones that have lost. It’s the mirror image of the sound rule “cut your losses and let your winners run.”
It systematically trims your strongest positions early while letting weak ones linger, dragging on returns over time. It also means the sell decision is being driven by how a trade feels — the comfort of a locked-in gain, the discomfort of a realised loss — rather than by whether each position is still worth holding on its merits.
A trailing stop follows a rising price up and only triggers a sale if the position falls back by a set amount. That directly counters the urge to clip a winner too soon: it lets the gain keep running while automatically protecting it, so a rule — not the itch to “book the win” — decides when you exit.
Investor education only — not investment advice, and never a promise of profit. Every investment can lose value.