Herd Mentality in Investing: Why the Crowd Loses Money

Show a group of people three lines of obviously different lengths, ask which one matches a fourth, and most will get it right every time. Now seat one real person among actors told to give the same wrong answer out loud first. In Solomon Asch's 1951 experiment, the real subject went along with the clearly wrong majority about a third of the time, and roughly three in four caved at least once across the trials. In a control group with no social pressure, the error rate was under 1%. People can see the right answer and still say the wrong one, because everyone around them did.

Markets take that instinct and turn up every dial. The right answer is rarely obvious, the crowd is loud, and being publicly wrong costs real money. That is the soil herd mentality grows in.

What is herd mentality in investing?

Herd mentality in investing is the habit of making decisions based on what the crowd is doing, instead of on your own read of the asset. You buy because others are buying, sell because others are selling, rotate into whatever sector is hot, and follow whichever name is trending. The crowd, not the cash flows, becomes the signal.

It helps to separate herd mentality from the general idea of a crowd fad. A fashion trend costs you a bad jacket. Herding in markets moves prices far from what the underlying businesses are worth, and then reverses, so the people who joined last take the losses. Asch explains the base instinct, the pull to agree with the group. Markets add two forces the psychology lab did not have: money on the line, and the belief that the people already in must know something you don't.

What are the two kinds of herding?

Herding comes in two flavors, and telling them apart is the whole game: informational herding, where copying is a rational bet that others know more, and reputational herding, where following is simply safer for you. Almost no explainer separates these cleanly, yet the difference decides whether a crowd is smart or dangerous.

Informational herding is the information cascade. Economist Abhijit Banerjee modelled it in a 1992 paper, "A Simple Model of Herd Behavior." Picture buyers deciding one after another, each seeing the choices made before them. The first acts on her own hunch. The second, seeing the first buy, leans that way even if her own hunch was weaker. By the third or fourth, the observed choices outweigh any private doubt, so everyone rationally copies, and the original hunch, which might have been wrong, gets locked in. Nobody behaved irrationally. The crowd still ended up wrong. Bikhchandani, Hirshleifer and Welch extended the same maths that year to fashions and fads generally.

Reputational herding is about your own skin. John Maynard Keynes put it plainly in 1936: it is better to fail conventionally than to succeed unconventionally. A fund manager who owns what everyone owns and is wrong keeps her job; one who bets against the room and is wrong does not. That asymmetry pushes even skilled professionals toward the consensus, which is why herding shows up in institutional money too, well beyond first-time retail accounts.

Why do smart people follow the crowd?

Rational people herd because, in the moment, copying looks like the safe and sensible move, not because they are foolish. Four pulls do most of the work.

Uncertainty is the trigger. When the right answer is genuinely unclear, the actions of others feel like free information, so borrowing the crowd's judgement seems efficient. Social proof is the reflex Asch measured, the discomfort of being the lone dissenter. Speed and volume are new: a stock tip now travels through WhatsApp forwards, Telegram channels and Instagram reels in minutes, so a cascade that once took weeks can form over a weekend. And reputational safety, the Keynes point, means that for anyone managing other people's money, moving with the pack is easier to defend than a solo call.

Notice what is missing from that list: stupidity. Every pull is a shortcut that usually works in ordinary life. It misfires in markets precisely because prices reflect what the crowd already believes, so by the time a move is obvious, it is often already expensive.

Herd mentality in the Indian market

India offers some of the cleanest herd episodes anywhere, because retail participation has exploded while the same crowd signals keep repeating. The pattern is older than social media and newer than last quarter.

Episode	What the crowd did	The reversal
Harshad Mehta run, 1991 to 1992	Retail investors followed the "Big Bull" as the Sensex tripled from about 1,100 toward 4,467	Sensex crashed to about 2,529 by August 1992, a fall of over 43%
SME IPO frenzy, 2024	HOAC Foods (NSE SME) drew bids worth about 1,834 times the shares on offer in May 2024	Many SME listings later gave up their pop as the frenzy cooled
Social-media pump-and-dump, 2024 to 2025	Crowds bought thinly traded stocks on unverified tips	SEBI barred 222 individuals and 5 entities and levied about 47.7 crore rupees in penalties
Penny-stock mania, 2024	Shri Adhikari Brothers rose about 76,450% in a year despite a loss-making core	Fundamentals that thin cannot hold a crowd forever

The Harshad Mehta case is the textbook one. Salaried people, retirees and first-timers piled in because everyone else was, on an index rising on story more than earnings, and the ones who bought near the top wore the crash. The SME IPO of 2024 is the modern rhyme: an oversubscription of about 1,834 times is not a considered valuation, it is a crowd sprinting through a narrow door. For the individual fear that pulls people into these, the crypto tips and the "everyone's getting rich" feeling, see our FOMO investing explainer, which is the emotion side of the same coin.

The US and global version

The Western herd episodes are the ones every finance page quotes, and they run from a 17th-century flower to a video-game retailer. They matter here because they show the mechanism is universal, and hardly an emerging-market quirk.

Tulip mania in 1630s Holland is the origin story, bulbs bid to the price of houses before collapsing. The dot-com bubble is the modern classic: the Nasdaq Composite peaked at 5,048.62 on 10 March 2000, then fell roughly 78% into its October 2002 trough as the crowd that had chased anything with ".com" in the name rushed out together. The 2008 crisis layered professional herding into mortgage securities on top of retail buying. And the GameStop squeeze of January 2021 flipped the usual script: a retail crowd on Reddit, not institutions, drove the stock to an intraday 483 dollars on 28 January against short interest of roughly 140% of the float.

Same arc every time. A story spreads, the crowd bids an asset far past what it is worth, and the exit, when it comes, is as crowded as the entrance.

What does herd mentality actually cost?

The cost of herding is measurable, and in India it is large: SEBI found that 93% of individual traders in equity F&O lost money over FY22 to FY24, with aggregate losses above 1.8 lakh crore rupees. That is a crowd-driven activity, spread through the same social channels, producing losses for more than nine in ten participants. The individual-psychology side of that number sits in our FOMO investing post; here it stands as the price tag on moving with the pack.

The subtler cost shows up even for long-term investors. Morningstar's 2024 "Mind the Gap" study found the average dollar in US funds earned about 7.0% a year over the decade to December 2024, roughly 1.2 percentage points behind the 8.2% the funds themselves returned, with the gap widest in the most volatile, most-chased funds. Morningstar frames that as around 15% of returns lost to badly-timed buying and selling. That framing is contested, some academics argue it overstates the timing cost, but the raw gap between what funds returned and what their investors kept is hard to wave away. Buying after a fund is popular and selling after it stumbles is herd behavior with a receipt.

How can you spot herd mentality in your own decisions?

You can catch herd-driven positioning by asking whether your reasons survive without the crowd. These are just signals, and none of them tell you what to do with your money, only where the crowd may be steering it.

• The reason you can give for buying leans on what others are doing more than on the asset itself.
• The idea arrived through a WhatsApp forward, a reel, a Telegram call or a headline, well before the company's own disclosures.
• You would not want the holding if its price had dropped 30% and the chatter had gone quiet.
• The stronger feeling is fear of being the only one left out.
• You find it hard to write down, in a sentence, what would make you sell.

If several of these ring true, the position is being shaped by the crowd. What to actually do about your own portfolio is a question for a SEBI-registered investment adviser, who can look at your full situation, which no checklist can.

What breaks herd behavior without turning you into a contrarian?

The counter to herding is not blind contrarianism, which is just the herd inverted, but structured independent judgement. The research and the disciplined-investor playbooks point to the same few defences, described here so you can recognize them, not as instructions.

A written investment thesis is the first. Committing to paper what an asset is, why, at what price and what would trigger a sale forces reasoning that "everyone's buying it" cannot fake. Source isolation is the second: consensus arrives loudest through live feeds, so reading primary material like company filings and regulator reports carries less social-proof charge than a scrolling timeline. Calibration tracking is the third, keeping an honest log of decisions and outcomes. Some investors, after tracking their own results, conclude that a broad-market index removes most of the bias surface area for them; whether that fits any individual is exactly the kind of judgement a qualified adviser exists for.

None of this makes anyone immune. It makes the crowd's influence visible, which is the part herding depends on staying hidden.

How herd mentality connects to FOMO and the other biases

Herd mentality rarely travels alone. It interlocks with FOMO investing, the individual fear that drives someone into a rising crowd; with loss aversion, which makes the panic-selling side of a crash feel urgent; and with anchoring, which fixes people on a crowd's price as if it were fair value. The clean split worth keeping is this: FOMO is the individual emotion, herd mentality is the crowd mechanism that amplifies it, one is fear-driven and the other conformity-driven. For how all of these biases fit together, the behavioral finance explained pillar maps the whole set.

What this post deliberately does not cover

This is an explainer on what herd mentality is and how it shows up in markets, not advice on your holdings. It doesn't tell you whether to buy or sell any asset, doesn't recommend index funds or active funds over each other, and doesn't forecast any market. The individual emotion of chasing gains is covered in the FOMO post; the cross-bias synthesis lives in the pillar page. Investing decisions depend on your goals, horizon and risk capacity, so anything touching your actual money is a conversation for a SEBI-registered investment adviser or a qualified financial planner.

Frequently asked questions

What is herd mentality in investing in simple terms? Herd mentality in investing is making decisions based on what other investors are doing rather than on your own analysis of the asset: buying when everyone buys, selling when everyone sells, piling into whatever sector or stock is popular. The pull is the same social conformity Solomon Asch measured in 1951, when people agreed with an obviously wrong majority about a third of the time. In markets it is amplified by information cascades (assuming earlier buyers knew something) and reputational safety (following the crowd is easier to defend than standing apart). The result is collective decisions that reliably lag the right answer.

How is herd mentality different from FOMO investing? FOMO is the individual emotion; herd mentality is the crowd mechanism that amplifies it. FOMO is fear-driven, the sting of watching others make money without you, and it can push you to break from your own group. Herd mentality is conformity-driven, the comfort of moving with the group, and it keeps you inside the crowd, including on the panic-selling side of a crash. The two often fire together, but the fix differs, which is why we cover the individual side separately in our FOMO investing explainer.

What are real examples of herd mentality in the stock market? In India, the 1992 Harshad Mehta episode saw retail investors pile in as the Sensex tripled, then lose heavily when it crashed over 43%; more recently, SME IPOs like HOAC Foods were subscribed about 1,834 times in May 2024. Globally, the classic cases are 17th-century tulip mania, the dot-com bubble (the Nasdaq fell roughly 78% from its March 2000 peak), the 2008 mortgage crisis, and the GameStop squeeze of January 2021, when the stock hit 483 dollars. Each shows the same arc: a crowd bids an asset far past its fundamentals, then rushes the exit together.

How can I tell if I am following the herd? A few honest questions surface it. Can you explain why you are buying without mentioning what other people are doing? Did the idea come from a WhatsApp group, a reel, or a headline, well before the company's own filings? Would you still want it if the price had fallen 30% and nobody was talking about it? Are you buying mainly because you are afraid of being the only one left out? If the reasons lean on the crowd, that is herd-driven positioning. Independent analysis of your money is a conversation for a SEBI-registered adviser, not a crowd.

In summary

Herd mentality is the oldest force in markets wearing new clothes each cycle. The mechanism has not changed since tulips: a story spreads, copying feels rational because others might know more and safer because standing apart is lonely, and the crowd bids an asset past what it is worth until the exit gets crowded. Asch showed the instinct in a lab, Banerjee showed why even rational people cascade into it, and India's own record, from Harshad Mehta to 1,834-times-subscribed SME IPOs, shows it never really left.

What separates the people who get trampled from the people who don't is not cleverness or contrarianism. It is whether their reasons survive the question "would I still do this if nobody else were?" The crowd's grip depends on that question never getting asked.

Sources

• Saul McLeod, Asch Conformity Experiments (1951), Simply Psychology: simplypsychology.org/asch-conformity.html
• Abhijit V. Banerjee, A Simple Model of Herd Behavior, Quarterly Journal of Economics, Vol. 107, No. 3 (1992)
• Bikhchandani, Hirshleifer and Welch, A Theory of Fads, Fashion, Custom, and Cultural Change as Informational Cascades, Journal of Political Economy, Vol. 100, No. 5 (1992)
• Securities and Exchange Board of India, Updated Study on Individual Traders in Equity F&O (FY22 to FY24), 23 September 2024: sebi.gov.in press release
• Morningstar, Mind the Gap 2024: morningstar.com
• Business Standard, HOAC Foods India SME IPO subscribed 1,834 times, May 2024: business-standard.com
• GameStop short squeeze, reference overview: en.wikipedia.org/wiki/GameStop_short_squeeze
• John Maynard Keynes, The General Theory of Employment, Interest, and Money (1936), chapter 12