Investors are quicker to sell what has gone up than what has gone down, everywhere, for decades, and at a real cost to themselves.
Few findings in behavioral finance are as well established, or sound as unremarkable on first hearing. When investors decide to sell something, they're far more likely to sell a position that's up than one that's down. Winners get realized, losers get kept. This has a name, the disposition effect, and it shows up so reliably, across so many markets and so many kinds of investors, that nobody seriously disputes it exists anymore.
Hersh Shefrin and Meir Statman named and described the pattern in the 1980s, borrowing the idea of a reference point from prospect theory to explain why investors seemed to treat gains and losses so differently from the way a rational calculator would. Terrance Odean later confirmed it in actual brokerage data, examining thousands of accounts and finding that investors realized gains at a much higher rate than losses. Since then it's turned up among professional traders who should know better, and among investors in countries with completely different tax codes and cultural norms.
On its face this makes no sense. What you happened to pay for something has no bearing on whether it's worth owning today. The company has no idea what price you paid. Whether to keep holding should depend on prospects relative to the current price; your personal cost basis is irrelevant to that question, full stop.
And yet the purchase price carries enormous psychological weight, because it becomes the yardstick investors use to judge themselves. A position above that price is a decision vindicated; selling it locks the vindication in, makes it permanent. A position below that price is a decision that looks like a mistake, and selling it turns a paper loss into a confirmed one. The reluctance has nothing to do with the stock. It's about not wanting to admit you were wrong.
That's why knowing about the bias doesn't cure it. An investor who fully understands the logic, who has resolved not to fall for it, will still find that closing a losing position feels much worse than closing a winning one, and the feeling doesn't listen to the argument. This isn't a failure to understand the math. It's that the understanding never reaches the part of the brain actually making the call.
The cost has been measured directly, not just inferred from theory. Because the effect leads investors to keep their weakest positions and sell their strongest, it works against them anywhere recent performance tends to persist even a little, and the evidence suggests it does, over certain stretches of time. Studies tracking what happened afterward to the stocks investors sold versus the ones they kept generally find that the sold stocks went on to do better than the ones left in the portfolio. That is exactly backward from what a sensible seller would produce.
There's an objection worth taking seriously, because it's the exact rationalization the bias uses to defend itself. An investor might say that holding onto a loser is just sound value investing: the price fell, the business didn't change, so it's now a better bargain. Sometimes that's true. But there's a simple test that separates real value reasoning from the disposition effect at work. A genuine value investor would happily buy more at today's price. Someone caught in the disposition effect wouldn't buy more; they just can't bring themselves to sell either.
That test is worth applying rigorously, because anyone can use it and it cuts through a lot of self-deception. Looking at a losing position, ask: if I held nothing at all and came across this stock today, at this price, would I buy it? Yes means holding is defensible. No means the only thing keeping you in the position is what you originally paid, a fact about your own history, not about the stock.
The effect also collides badly with taxes. Where gains are taxed and losses can offset them, the sensible order of operations is often the reverse of what investors actually do. So the disposition effect doesn't just cost money through bad timing, it frequently costs extra in taxes on top of that.
The defenses here are ordinary, not clever. Deciding in advance, in writing, what would make you reconsider a position takes the decision out of the moment when the purchase price has the strongest grip. Reviewing a portfolio by asking what you'd buy today, rather than by staring at gains and losses against cost, reframes the question in the only terms that actually matter. Neither trick makes the pull disappear. They just move the decision somewhere the pull can't reach.
The passage of time makes this worse, not better. A losing position that's held onto doesn't get easier to sell as the loss grows, it gets harder, because the size of the admission grows with it. Someone who couldn't accept a small loss will find a large one even tougher to swallow, so the position becomes more entrenched exactly as the case for selling it gets stronger. Nothing about this fixes itself. An investor who plans to deal with a loser later has usually, without realizing it, decided never to deal with it.
VESTFY™ points to the disposition effect as the clearest case of a bias that knowledge alone doesn't fix. Understanding it doesn't make the feeling go away, it just lets you recognize the feeling for what it is, and build rules that don't depend on you winning a fight with your own instincts in the moment.