Anchoring Bias in Trading: How Old Prices Wreck Indian Trades

What anchoring bias actually is

Anchoring bias is the tendency to lean too hard on the first number you see and then adjust away from it too little. The term comes from a landmark 1974 study by Amos Tversky and Daniel Kahneman, published in the journal Science as Judgment under Uncertainty: Heuristics and Biases. Kahneman later won the Nobel Memorial Prize in Economics in 2002 for this broader body of work on how people really make decisions under risk.

In one famous experiment, Tversky and Kahneman spun a rigged wheel of fortune that stopped on either 10 or 65, then asked people what percentage of African countries are in the United Nations. People who saw 10 guessed about 25 percent on average. People who saw 65 guessed about 45 percent. The wheel number was random and had nothing to do with the question, yet it dragged the answers with it. That is anchoring in its purest form, and a stock price on your screen is a far stronger anchor than a roulette wheel.

For a trader, the dangerous part is that the anchor feels like information. Your entry price of Rs 1,420 on Reliance feels like it tells you something about what the stock is worth. It does not. It only tells you what you paid. The market does not know or care about your cost, and a stock that has fallen to Rs 1,250 is worth Rs 1,250 to a fresh buyer, regardless of where you got in.

The four anchors that cost Indian traders money

Anchors are everywhere on a trading screen. The four that do the most damage to retail traders on the NSE and BSE are the entry price, the round number, the recent high, and the old target. Each one quietly turns a forward-looking decision into a backward-looking one.

• Your entry price. The single strongest anchor. It splits every position into a winner or a loser in your head, when the only question that matters is whether the trade is still worth holding from today's price.
• Round numbers. Nifty 25,000, Bank Nifty 55,000, Reliance Rs 1,500, gold near a fresh high. Round numbers attract clustered orders, which is partly why support and resistance form there, but they also trap you into selling or buying purely because a digit changed.
• The 52-week high or recent high. A stock that hit Rs 4,200 and now trades at Rs 3,400 feels cheap, even if Rs 4,200 was an overvalued spike that should never be your reference point.
• An old analyst target or IPO price. A brokerage target of Rs 900 set six months ago, or an IPO list price, sticks in memory long after the company's fundamentals and the market have moved on.

A worked example: anchoring on Reliance shares

Numbers below are illustrative and not a recommendation. Suppose you buy 200 shares of Reliance Industries at Rs 1,420, an outlay of Rs 2,84,000. A weak quarterly result and a sector downgrade push the stock to Rs 1,300. Your plan, written before you entered, was a stop-loss at Rs 1,350. But Rs 1,420 is now your anchor, so instead of exiting you tell yourself you will sell when it gets back to break-even.

The stock keeps sliding to Rs 1,180 before you finally give up. By anchoring to Rs 1,420 you turned a planned loss of about Rs 14,000 (200 times Rs 70) into a realised loss of Rs 48,000 (200 times Rs 240). The anchor did not protect your capital, it cost you an extra Rs 34,000. Since these are delivery equity shares held under a year, that becomes a short-term capital loss you can set off against short-term capital gains, which are now taxed at 20 percent after the July 2024 Budget change. A loss is never a good tax plan.

The lesson is not that Rs 1,350 was a magic level. It is that you decided the level before you had skin in the game, when no anchor was pulling on you, and then you let the anchor override your own earlier, calmer judgment.

Anchoring in Nifty and Bank Nifty options

Options magnify anchoring because the premium you paid is so vivid, and because time decay (theta) erodes value every day whether the stock moves or not. Traders anchor to the entry premium and refuse to cut a losing option, forgetting that an out-of-the-money option's value bleeds to zero as weekly expiry approaches.

Illustrative example. Nifty is at 24,900 and you buy one lot of the weekly 25,000 call at a premium of Rs 120. The Nifty options lot size is 65, so you pay 75 times Rs 120, which is Rs 9,000 plus charges. Two days later Nifty has drifted to 24,820 and your 25,000 call is now worth Rs 55. You are down 75 times Rs 65, about Rs 4,875. Your anchor of Rs 120 makes you hold, hoping for a bounce back to Rs 120. But with expiry on Tuesday and the strike now further out of the money, theta is against you. The honest question is not whether it returns to Rs 120, but whether, starting fresh today at Rs 55, you would buy this call at all. Usually the answer is no, and holding just feeds the decay until the option expires worthless and you lose the full Rs 9,000.

How anchoring differs from related biases

Anchoring is often confused with other behavioural traps that Tversky, Kahneman and later researchers documented. They overlap, but they are not the same, and naming the right one helps you fix it.

These often stack on top of each other. A trader anchored to entry price (anchoring) feels the unrealised loss too sharply (loss aversion) and then reads only the bullish takes that justify holding (confirmation bias). The compounding is why behavioural mistakes feel so convincing in the moment.

Why your brain anchors, and why it is hard to switch off

Tversky and Kahneman argued that anchoring is a by-product of a normal mental shortcut. When facing an uncertain estimate, the mind grabs a convenient starting value and adjusts from there, but the adjustment is almost always too small. Their later work, including Kahneman's book Thinking, Fast and Slow, framed this as the fast, automatic part of the mind producing a quick answer that the slow, deliberate part rarely overrides hard enough.

Knowing about anchoring does not immunise you against it. In follow-up studies, even experts who were explicitly warned still anchored. That is the key practical insight for traders: you cannot out-think this bias in real time with willpower alone. The fix has to be structural, built into rules and routines that act before the anchor can grab the wheel.

A practical system to beat anchoring

Because the bias is automatic, the only reliable defence is to make your key decisions in advance, in writing, when no position is pulling on you. The goal is to replace a remembered anchor with a pre-committed rule.

• Write the exit before the entry. Define your stop-loss and target in rupees or percent at the moment you plan the trade, not after you are in it. A trade plan made under the influence of a live profit and loss is already compromised.
• Judge from today's price, not your cost. Hide your buy price if you can. Many traders re-evaluate positions far more rationally when the cost column is out of sight.
• Use the fresh-eyes question. For every open position, ask whether you would open it again right now at the current price. If not, you are holding out of anchoring, not conviction.
• Keep a trading journal. Record your entry reason, your planned exit, and your actual exit. Over a month you will see exactly how often the gap between plan and action was caused by clinging to an old price.
• Set alerts on levels, not on your cost. Anchor your attention to a technical level or a thesis-invalidation point, never to break-even.

Anchoring at the index level: rounds numbers and the news

Anchoring is not only personal, it shows up across the whole market. Round index levels such as Nifty 25,000 or Sensex 80,000 become shared anchors. Order books cluster there, financial headlines obsess over them, and traders treat them as meaningful walls when they are mostly psychological. A break above or below a big round number often gets an outsized reaction simply because so many people anchored to it at once.

Macro events sharpen this. When the Reserve Bank of India holds or changes the repo rate, or a Union Budget lands, traders frequently anchor to the index level just before the announcement and judge everything against that pre-event mark, instead of asking what the new information actually changes about earnings and rates. The anchor is the old level, the reality is the new fundamentals, and the gap between them is where avoidable losses live.

Putting it together

Anchoring bias, first named by Tversky and Kahneman in 1974, is one of the most reliable ways for a disciplined trading plan to quietly fall apart. The anchor, usually your own buy price, feels like a fact but is just a memory, and it pulls your sell, hold and add decisions toward the past when they should be facing the future.

You will not reason your way out of it in the heat of a moving market, so build the defence into your process instead. Decide exits before entries, evaluate every position as if you held no cost basis at all, and keep a journal that shows you the rupee cost of every time the anchor won. Do that consistently and the bias stops being a leak in your account and becomes just a quirk of how brains handle numbers.

Frequently asked questions

Sources and Further Reading

For authoritative data and further reading on this topic, refer to Zerodha Varsity, Investopedia and SEBI Investor Education. Always confirm current rules, rates and contract specifications on the official source before you trade.