Updated August 2026 · Mike Shell, Chief Investment Officer

The disposition effect is the documented tendency of investors to sell winning positions too early and hold losing positions too long. It is loss aversion expressed as behavior, and it manufactures negative asymmetry out of an otherwise sound portfolio.

Every investor knows to cut losses and let winners run. Almost none of them do it.

Why it matters. Hersh Shefrin and Meir Statman named the effect in 1985, and Terrance Odean’s later work on thousands of individual brokerage accounts confirmed it empirically: investors were substantially more likely to realize a gain than an equivalent loss, and the winners they sold went on to outperform the losers they kept. The mechanism is straightforward once you see it. Selling a loser converts a paper loss into a permanent, acknowledged mistake, which is psychologically expensive. Selling a winner books a gain and removes the anxiety of watching it evaporate. Both impulses are comfortable, and together they invert the ratio a portfolio depends on. This is not an error of analysis. It is an error of execution committed by people whose analysis was fine.

The math. Suppose a portfolio produces gains averaging 8% when it wins and losses averaging 8% when it loses, with a 50% hit rate — break-even, before costs. Now apply the disposition effect: winners get sold at 4% because the gain felt worth protecting, and losers get held to 16% because selling meant admitting the mistake. The hit rate has not changed at all. But the portfolio now averages 4% on winners against 16% on losers, and it loses roughly 6% per pair of positions. Nothing about the selection improved or deteriorated. The entire result was produced by the exit decisions, which is why the exit is the part of the process that actually determines outcomes.

How it’s applied in ASYMMETRY® Managed Portfolios. The defense is procedural, because insight into the bias does not protect against it. Every position enters with a predefined exit set before there is any money at stake and any feeling attached to the outcome — which moves the decision from the moment of maximum pressure to a moment of calm. On the other side, a profitable position is not trimmed simply for being profitable; an unrealized gain is not information and is not a reason to act. Winners are given room and exits are trailed rather than tightened out of nervousness. The whole architecture exists to enforce a shape that no one produces naturally, which is the honest reason systematic processes outperform discretion over a full cycle.

Common misconceptions. The disposition effect is not the same as taking profits, which can be entirely rational when a position reaches a predetermined objective — the effect is specifically taking them early, driven by discomfort rather than by plan. It is not the same as conviction: holding a loser because a written thesis remains intact is a decision, while holding one because selling would hurt is a symptom, and the difference is whether the level was defined in advance. It is not confined to individual investors, since institutional desks and committees display it too. And it is not corrected by awareness. The effect survives being explained, which is why it has to be handled with a rule rather than with resolve.

Related terms. Loss aversion — the underlying bias. Prospect theory — the research framework. Negative asymmetry — what the behavior produces. Predefined risk, investor behavior, and asymmetric bet follow in the lexicon. Part of the ASYMMETRY® guide to asymmetric investing.

Mike Shell is the Founder and Chief Investment Officer of Shell Capital Management, LLC, and portfolio manager of ASYMMETRY® Managed Portfolios, with nearly three decades of live-market experience across multiple full market cycles.