Anchoring Bias in Investment Decisions

The First Number You See Sticks — Even When It's Irrelevant

In a famous experiment, researchers spun a wheel rigged to land on either 10 or 65, then asked people what percentage of African countries are in the United Nations. Those who saw 65 guessed much higher than those who saw 10 — even though the wheel was obviously random and had nothing to do with the question. That's anchoring: the first number we encounter quietly drags our judgment toward it, whether or not it has any relevance.

Investing is full of these arbitrary anchors, and the most powerful one is the price you happened to pay. Your purchase price feels enormously significant — it's the reference point against which you mentally book a gain or a loss. But the market has no idea what you paid and cares even less. A stock that you bought at $100 and that now trades at $70 is a $70 asset, full stop. What you paid is history; it tells you nothing about what the asset is worth today or where it goes next.

The Purchase Price: The Most Expensive Anchor of All

Anchoring on your purchase price produces two costly behaviors. First, it makes people refuse to sell at a loss: "I'll sell once it gets back to what I paid." The asset doesn't know your break-even price and is under no obligation to return to it, so this is just a wish dressed up as a plan, and it keeps capital trapped in a poor holding waiting for a number the market never agreed to. Second, it makes people too quick to dump winners — selling simply because a stock has "doubled from what I paid," as if the purchase price set a ceiling.

The clean test is to ask: if I held this position as cash today, would I buy this asset at its current price? If yes, hold it. If no, sell it — regardless of whether that locks in a gain or a loss relative to what you paid. Your purchase price should have zero weight in that decision. It's a fact about your past, not about the asset's future, and treating it as meaningful is one of the most common and expensive anchors in investing.

Round Numbers, All-Time Highs, and Other Phantom Anchors

The purchase price isn't the only anchor at work. Round numbers exert a strange gravity — investors treat a market index crossing 5,000 or a stock hitting $100 as meaningful thresholds, when these are just artifacts of the number system with no bearing on value. All-time highs anchor people too: "it was $200 last year, so $140 is cheap" assumes the old high was the correct price, which it may never have been.

Analyst price targets and 52-week highs and lows function as anchors as well, framing your sense of "cheap" and "expensive" around numbers that may be arbitrary. The defense is the same in every case: ask what the asset is actually worth today based on its fundamentals and your goals, and notice when a number is influencing you only because it's salient — round, recent, or remembered — rather than because it's relevant.

• Purchase price: 'I'll sell when it's back to what I paid' — the market doesn't know or care what you paid.
• Round numbers: an index at 5,000 or a stock at $100 is an artifact of arithmetic, not a meaningful level.
• All-time highs: 'it was $200, so $140 is cheap' assumes the old high was ever the right price.
• 52-week range and price targets: salient numbers that frame 'cheap' and 'expensive' for you arbitrarily.

How to Stop Anchors From Steering You

The most reliable cure is to invest in a way that never asks the anchoring question at all. Broad, diversified index funds like VOO or VTI, bought on an automatic schedule, make your purchase price irrelevant by design — you're buying the whole market across many price points over years, not staking a thesis on one entry level you'll then anchor to. Dollar-cost averaging dissolves the single purchase price into an average, removing the anchor before it can form.

For any decision where an anchor might be lurking, run the cash test: would I buy this today, at today's price, knowing what I know now? Make the decision on that basis and deliberately ignore what you paid, what it hit last year, and what round number it's near. Anchors are hard to delete from your mind, but you can refuse to let them cast a vote. The investors who avoid this trap aren't immune to the pull of the first number — they've just trained themselves not to act on it.