Behavioral Finance · Cognitive Bias
Anchoring Bias in Finance
Why the first number you encounter distorts every financial judgement that follows — and how anchoring silently shapes asset prices, valuations, and investor behaviour.
In a famous experiment, Tversky and Kahneman (1974) asked participants to estimate the percentage of African nations in the United Nations. First, they spun a wheel rigged to land on either 10 or 65. Participants who saw 65 guessed significantly higher numbers than those who saw 10 — even though the wheel spin was completely random and obviously unrelated to the answer. This is anchoring — and it is one of the most powerful and pervasive cognitive biases in all of finance.
📘 Key Term
Anchoring Bias is the cognitive tendency to rely too heavily on the first piece of information encountered (the ‘anchor’) when making decisions. Subsequent judgements are then made by adjusting from this anchor — but adjustments are typically insufficient, leaving final estimates biased toward the initial number, even when it is arbitrary or irrelevant.
How Anchoring Works: The Psychology
Anchoring operates through two distinct psychological mechanisms, identified by Epley and Gilovich (2006):
Selective Accessibility: When an anchor is presented, it activates anchor-consistent knowledge in memory, biasing the information retrieved when making the estimate. If the anchor is ‘high’, high values become more cognitively accessible.
Insufficient Adjustment: Even when people know an anchor is irrelevant, they adjust from it rather than reasoning from scratch — and these adjustments consistently stop too early, leaving estimates anchored to the starting point.
Anchoring in Financial Markets: 5 Key Manifestations
1. Purchase Price Anchoring
Investors anchor to the price they paid for an asset. They refuse to sell at a loss relative to purchase price — even when holding is economically irrational. This is the foundation of the disposition effect and causes significant under-realisation of losses in investor portfolios.
2. 52-Week High/Low Anchoring
Investors treat a stock’s 52-week high as a reference point for ‘fair value’. Research shows that stocks trading near their 52-week high tend to receive lower analyst price targets than fundamentals justify — because analysts anchor to the recent high rather than the intrinsic value.
3. IPO Price Anchoring
Investors anchor to the IPO offer price when evaluating whether a new stock is ‘cheap’ or ‘expensive’ in early trading. This creates predictable patterns in post-IPO price dynamics — underperformance relative to anchor-naive valuations is well documented.
4. Analyst Earnings Anchoring
Analysts anchor their earnings forecasts to prior-period earnings or consensus estimates. This causes herding in forecasts and generates predictable earnings surprise patterns — stocks that beat anchored consensus estimates systematically outperform, creating a durable momentum anomaly.
5. Negotiation and Valuation Anchoring
In M&A negotiations, the first offer sets the anchor. Acquirers who name a first bid gain significant advantage over those who respond — the entire negotiation proceeds relative to that anchor. This is why investment bankers carefully manage the anchoring of initial valuations.
💡 Key Insight
Anchoring is particularly dangerous because it affects experts as much as novices. Studies show that experienced financial analysts and auditors are just as susceptible to anchoring effects as untrained participants. Expertise does not protect against anchoring — awareness and structured de-biasing techniques are required.
⚠️ Common Error
Students sometimes confuse anchoring with reference dependence from Prospect Theory. Both involve reference points, but they are distinct: reference dependence determines how outcomes are valued (gains vs losses); anchoring determines how estimates and judgements are formed. An investor’s purchase price can simultaneously serve as a Prospect Theory reference point (determining how gains and losses are felt) AND as an anchor (biasing estimates of fair value). The two effects can operate together.
Q1. A firm’s shares traded at £200 twelve months ago and now trade at £80. Explain, using anchoring theory and Prospect Theory, why individual investors may be reluctant to sell at the current price. [8 marks]
Answer: Two behavioural mechanisms operate simultaneously. First, anchoring: investors anchor to the historical price of £200 and perceive the current price of £80 as implying the stock is ‘undervalued’ relative to this anchor — they expect mean reversion to their reference point. This delays selling as investors wait for a price recovery. Second, Prospect Theory reference dependence and loss aversion: investors evaluate the current position as a loss of £120 relative to their reference point (purchase/historical price). Loss aversion (λ ≈ 2.25) means this loss feels approximately 2× more painful than an equivalent gain would feel pleasurable — making selling at £80 psychologically aversive. Investors prefer to hold, avoiding the realisation of the loss. Together, anchoring and loss aversion create strong inertia against selling, even when the expected return from holding is inferior to alternative investments.
References
1. Tversky, A. and Kahneman, D. (1974) ‘Judgment Under Uncertainty: Heuristics and Biases’, Science, 185(4157), pp. 1124–1131.
2. Epley, N. and Gilovich, T. (2006) ‘The Anchoring-and-Adjustment Heuristic’, Psychological Science, 17(4), pp. 311–318.
3. George, T.J. and Hwang, C.Y. (2004) ‘The 52-Week High and Momentum Investing’, Journal of Finance, 59(5), pp. 2145–2176.
4. Northcraft, G.B. and Neale, M.A. (1987) ‘Experts, Amateurs, and Real Estate’, Organizational Behavior and Human Decision Processes, 39(1), pp. 84–97.
5. Kahneman, D. (2011) Thinking, Fast and Slow. Farrar, Straus and Giroux.