Anchoring Bias: Why You Can't Stop Comparing the Price to What You Paid
Your purchase price, an asset's all-time high, and round numbers all act as psychological anchors that distort what a fair price actually looks like. What anchoring bias is, the research behind it, and how to actually price an asset without one.
You bought at $80. It’s at $34 now. Somewhere in your head, $80 has quietly become “what this is worth” — the number every future price gets measured against, the number that makes $34 feel cheap and $60 feel like a win. The asset doesn’t know you paid $80. The market has no memory of your entry price. But your brain treats it as load-bearing information anyway, and that’s not a personal flaw — it’s one of the most reliably documented biases in how people make any numerical estimate, priced asset or otherwise.
This is anchoring bias: the tendency to lean on the first number you’re given, even an arbitrary one, when estimating an unknown quantity — and then adjust from it too little. In investing, the first number is rarely arbitrary in the way a lab experiment’s is, but it’s just as disconnected from what the asset is actually worth today.
The experiment that proved how little the anchor needs to matter
The original demonstration, from psychologists Amos Tversky and Daniel Kahneman’s landmark 1974 paper in Science, didn’t involve money at all. Subjects watched a wheel of fortune numbered 0 to 100 — secretly rigged to stop on either 10 or 65 — and were then asked an unrelated question: what percentage of countries in the United Nations are African? People who saw the wheel land on 10 guessed a median of 25%. People who saw it land on 65 guessed a median of 45%.
Everyone in the room knew the wheel was random. They’d watched it spin. It still moved their answer by 20 percentage points. That’s the core finding: an anchor doesn’t need to be relevant, credible, or even remembered as influential to shift a judgment. It just needs to be seen first.
Your purchase price is a far stronger anchor than a random wheel spin, because it isn’t random to you — it’s the number you committed real money to, which gives it emotional weight the wheel never had. That makes the distortion larger, not smaller.
Three anchors that hijack a price judgment
Your purchase price. This is the anchor most people notice, at least a little — the quiet math running in the background where every price gets measured as “up from what I paid” or “down from what I paid” rather than against what the asset is actually worth today. A stock at $34 isn’t inherently cheap or expensive; it only feels cheap relative to your $80 entry, which is a number the market has no reason to respect.
The 52-week high or all-time high. This one is less obvious and better studied. A 2004 paper in The Journal of Finance by Thomas George and Chuan-Yang Hwang, “The 52-Week High and Momentum Investing”, found that investors anchor their valuation of a stock to its 52-week high, and that nearness to that high explains a large share of subsequent momentum returns — more than past return patterns alone. In practice: an asset trading well below its 52-week high gets treated as “cheap relative to where it’s been,” while good news struggles to push the price back toward that high, because investors are anchored to it as a ceiling rather than pricing the news on its own terms. It’s the same mechanism as your entry price, just borrowed from the whole market’s memory instead of your own.
Round numbers. Bitcoin at $100,000, a stock at $50, an index at a clean 5,000 — round numbers act as anchors purely because they’re memorable and easy to reference, not because they carry any actual valuation signal. Watch how much psychological weight a “will it hold $X” round-number level gets in market commentary relative to an equally real but less memorable level like $48,720.
Why “it’ll come back to what I paid” isn’t a thesis
The tell that anchoring, not analysis, is driving a decision is simple: the target price in your head is a number you experienced, not a number derived from anything about the asset’s current fundamentals, growth prospects, or competitive position. “It’ll get back to $80 eventually” is a claim about your memory, not a claim about the business or the asset. Compare it to “it’ll get back to $80 because revenue is growing 30% a year and the multiple is currently compressed relative to peers” — the second claim happens to reference the same number, but the number is doing no work; the reasoning would hold at any entry price.
This is the same underlying test used in Down 50%? Here’s the Actual Plan: would you buy this asset today, at today’s price, with no history attached? Anchoring bias is specifically what makes that question hard to answer honestly — your brain keeps smuggling the old price back in as if it were relevant evidence.
A worked example
Say you bought a stock at $200. It’s now at $90 — down 55%. Two people look at the same $90 price:
Person A: “It’s down from $200, it’s cheap, it’ll come back.” The $200 is doing all the work here. Ask what specifically changed about the company’s earnings, competitive position, or growth outlook, and the honest answer is often “nothing I’ve actually checked recently” — the case rests entirely on the gap between two prices, one of which is private to this specific investor’s memory.
Person B ignores the $200 entirely and asks: at $90, what’s the current earnings multiple, how does it compare to peers trading at similar multiples, and has anything in the business itself deteriorated enough to justify the drop? If that analysis says $90 is a reasonable or even undervalued price on its own terms, that’s a real thesis — one that would be exactly as valid if the entry price had been $60 or $300 instead of $200.
Same asset, same price, same day. One judgment is anchored. The other isn’t. Only one of them tells you anything useful about what to do next.
How to actually break the anchor
Estimate blind, then check. Before looking at your purchase price, the 52-week high, or any round number, write down what you think a fair price is today, based only on current fundamentals. Only after you’ve committed to that number should you look at the anchors and see how far your gut estimate drifted toward them. If your blind estimate and your anchored instinct disagree by a lot, that gap is the size of the bias operating on this specific decision.
Restate the question without the number. Instead of “will it get back to $80,” ask “is this worth buying at $34 today, with no other information.” Removing the anchor from the sentence itself makes it much harder for your brain to smuggle it back in through the side door.
Treat round numbers and 52-week highs as other people’s anchors, not yours. It’s fine to notice that a lot of market participants are watching a round-number level — that’s a real, if secondhand, piece of information about how a crowd might behave near that price. It’s a different thing entirely to let that same level convince you the asset is fundamentally cheap or expensive relative to it.
What this doesn’t mean
None of this means your cost basis is irrelevant — it matters enormously for taxes, and knowing it precisely is the whole subject of the records you actually need to claim a capital loss. The point isn’t to forget what you paid. It’s to stop letting that number answer a question it has no information about: what the asset is actually worth from here. Those are two different jobs, and anchoring bias is specifically what happens when one number gets used for both.
FAQ
Isn’t it reasonable to think about what I paid when deciding whether to sell? Your cost basis matters for taxes — it determines your gain or loss and what you owe. It should have zero influence on what you think the asset is worth going forward. Those are two completely separate questions that anchoring bias tricks you into merging: one is an accounting fact for the IRS, the other is a forward-looking judgment the market doesn’t consult your purchase price to make.
How is anchoring different from loss aversion or the sunk cost fallacy? They overlap in practice but work differently. Loss aversion is about a loss feeling worse than an equivalent gain feels good. The sunk cost fallacy is about letting money already spent influence a decision that should only depend on what happens next. Anchoring is more basic than either — it’s a general-purpose flaw in how the brain estimates any number, not just money, where an irrelevant reference point distorts the estimate. Your purchase price can trigger loss aversion (it hurts to sell below it) and anchoring (it makes you misjudge fair value) at the same time, which is part of why the pull to hold feels so strong.
If anchors are so unreliable, why do so many traders use technical levels like the 52-week high or a round number as decision points? Because other market participants are anchored to those same levels, which makes them behave as real support and resistance zones — not because the level itself carries information about fundamental value. That’s a legitimate, if different, use of the concept: trading the fact that a crowd is anchored, rather than being anchored yourself. The distinction is whether you’re using the level to predict how other anchored people will react, or using it to judge what the asset is actually worth.
Can I train myself out of anchoring entirely? Not entirely — it’s a documented feature of how human judgment works, not a personal weakness you can will away, and it shows up even in people who know the research well. What you can do is build a process that doesn’t depend on willpower in the moment: forcing yourself to state a valuation before you look at any reference price, and treating any estimate you make while your purchase price or the asset’s all-time high is visible on screen as suspect until you’ve checked it against that blind estimate.