The Madness of Markets (Alex Edmans) | Rational Reminder 431

Summary

Alex Edmans discusses how investor psychology can create market mispricing—and why recognizing an anomaly does not guarantee that an investor can profit from it. Investors may overreact to dramatic news, overlook less visible information, follow the crowd, or anchor on irrelevant reference points. These patterns can support strategies such as value, reversal, and momentum, but they can persist or worsen before correcting. Patience, diversification, costs, and an investor’s actual edge are therefore crucial.

Market behavior and investor biases

• Mood can affect markets: Research cited by Edmans found that after a country was eliminated from the World Cup, its stock market fell about 0.5% the next day—approximately £15 billion for the UK market. Studies of unexpectedly sunny or cloudy weather also found associations with market movements. Edmans emphasizes that replication, broader data, and a plausible economic explanation help distinguish robust findings from spurious correlations.
• Crowds do not always cancel out: Unlike private guesses about the number of objects in a jar, market opinions can move together because of shared sentiment, social influence, and fear of missing out. Examples discussed include enthusiasm for AI, cryptocurrency, and NFTs, as well as behavior on Reddit’s WallStreetBets forum.
• Overreaction: Investors may react too strongly to either good or bad news. Edmans gives the example of Zoom shares rising about 700% during the pandemic, as investors may have overestimated how lasting lockdown-driven demand would be. He also describes an AI-related corporate rebranding whose stock reportedly rose 582%; the company name in the subtitles appears unreliable, so this example may be mistranscribed.
• Underreaction: Markets may be slow to price information that is less prominent or conflicts with existing beliefs. Edmans’s research on the 100 Best Companies to Work for in America found that listed companies outperformed peers by 2.3–3.8% annually over 28 years, or 89–184% cumulatively. He argues that investors may have overlooked the information because employee culture is hard to translate into conventional valuation models.
• Other decision errors: Investors may anchor on their purchase price, sell winners too early to “lock in” gains, and hold losers to avoid realizing losses. Round-number targets can also distort decisions; Edmans suggests not waiting for an arbitrary price such as $100 if the investment case already supports selling.

Strategies and frameworks discussed

Long-term reversal / contrarian strategy

• Rank stocks by performance over roughly the prior three years.
• Buy past losers and sell past winners.
• The rationale is that longer-run overreaction can reverse.
• Use fundamentals or intangible assets as a second check: a past loser may be cheap for good reason, not simply mispriced.

Value investing

• Compare valuation multiples—such as price-to-earnings (P/E)—among firms in similar industries or at similar stages of development.
• Buy relatively inexpensive securities and sell or avoid expensive ones, while considering whether differences in intangible assets, brands, or corporate culture justify different valuations.
• Edmans cites Cisco’s P/E of 190 in 2000, about three times Microsoft’s and four times Intel’s, as an example of an extreme relative valuation.

Momentum

• Rank stocks by returns over approximately the previous six months.
• Buy recent winners and sell recent losers, based on the idea that short-term underreaction can let trends persist.
• Momentum can also be applied at the sector or country level, potentially without analyzing each individual stock.
• Edmans says momentum tends to be strongest in small, less-covered stocks and in markets outside the US, where information may receive less attention.
• He cautions that momentum can suffer sharply during market stress, measured by a large S&P 500 decline or a high VIX. A study discussed in the interview suggests reducing or exiting momentum exposure in such conditions; the hosts note they do not know of a specific product that implements this timing approach.

Assessing an active strategy or manager

• Identify a credible edge—not merely a persuasive story or strong past returns.
• Evaluate the investment process and whether the manager’s strategy is understandable.
• Consider whether the fund has become too large to implement the strategy effectively.
• Account for fees and access terms: a strategy’s gross performance may not translate into investor returns after costs.

Diversification, market efficiency, and performance

• Edmans cites research finding that fewer than three in seven individual stocks outperformed Treasury bills over the period studied. Rounded to the nearest 5%, the most common individual-stock return was −100%. The market can still produce strong returns because a small number of exceptional winners generate a disproportionate share of gains.
• In 2023, the other 493 S&P 500 companies reportedly gained 12.5%, while the “Magnificent Seven” rose by more than 100%; the S&P 500 gained about 26%. The implication is that investors cannot know in advance which companies will become the next major winners, making diversification important not only to limit losses but also to capture future winners.
• Edmans says he holds more index funds than he once did, especially in developed markets such as the US, which he considers difficult to beat through active stock selection. He sees more potential for active management in emerging and frontier markets, though that is not a guarantee of outperformance.
• The hosts’ closing takeaway is that markets work, diversification is valuable, and costs matter. Index investing is presented as a reasonable choice for investors who cannot identify a reliable advantage. The discussion also recognizes a possible role for active strategies when an investor has genuine skill, a suitable time horizon, and favorable fees.
• An illustrative compounding example: a diversified portfolio earning 10% annually for 10 years grows by about 160%, not 100%, before considering costs and taxes.
• Edmans argues that long horizons can help individual investors withstand short-term losses that may force professional managers to close positions. He describes increasing his stock allocation by 20 percentage points in early 2009, with a stated 40-year horizon, and cites Clare College, Cambridge, investing £15 million in a fund with a 40-year horizon.

Market examples and inefficiencies

• Limits to arbitrage: A mispricing can become more extreme before it corrects. Edmans recounts Julian Robertson’s short position against late-1990s technology stocks: the bubble continued to inflate, investors withdrew funds, and Tiger Management was liquidated in March 2000, shortly before the bubble burst.
• Published anomalies may weaken but persist: Research by McLean and Pontiff, as summarized in the interview, found that anomaly profitability fell by about one-third after publication, rather than disappearing completely. Edmans attributes persistence partly to career risk and the tendency to prefer fashionable industries over less exciting ones.
• Repetition and confirmation bias: The interview describes EntreMed’s Angiostatin news, which had appeared in the New York Times six months earlier. When it received more prominent coverage, the stock reportedly rose sevenfold. Amazon’s early cloud-computing services, launched in 2006, were also discussed as information the market took time to recognize; the services were separately reflected in reporting in 2015.
• Law of one price: Identical or closely related assets may trade at different prices. Examples include Palm’s value exceeding that of its parent, 3Com; recently issued US Treasury securities trading at a premium to older securities with comparable remaining cash flows, partly because of liquidity; and index funds with different fees attracting investors based on historical performance or headline charges.
• “Big market” fallacy: Adding up the valuations of companies in a popular sector does not mean the sector’s total valuation is justified. Edmans says that, in the early 2020s, the electric-vehicle sector’s aggregate market value exceeded that of traditional automakers even though EV companies were generating only a fraction of their profits. He cautions that investors may price an entire sector as if many competing companies will all become winners.

Assets, companies, and sectors mentioned

• Stocks and companies: Tesla, Zoom, Microsoft, Google/Google Meet, Cisco, Intel, Amazon/AWS, Silicon Valley Bank, 3Com, Palm, Altria, Boeing, Nvidia, Enron, Tyco, and the “Magnificent Seven.”
• Sectors and themes: AI, technology, internet/telecom, cloud computing, cryptocurrency, NFTs, electric vehicles, genomics, green hydrogen, chemicals, tobacco, railways, defense, and corporate culture/workplace practices.
• Countries and regions: US, UK, Canada, India, and emerging/frontier markets.
• Funds and instruments: S&P 500 index funds and index mutual funds, Parnassus Workplace Fund/Parnassus Core Equity Fund, ARK funds, Dimensional strategies, Treasury bills and bonds, corporate bonds, cash, private equity, and the VIX.

Disclosures and cautions

No explicit “not financial advice” disclaimer appears in the subtitles. The discussion is educational and research-focused; the strategies described are not presented as guaranteed or suitable for every investor. The speakers stress that active investing requires an edge, that anomalies can be difficult to exploit in practice, and that fees, capacity, timing, and investor patience can determine whether a strategy benefits its holders.

Presenters and sources

Presenters: Ben Felix and Cameron Passmore. Guest: Alex Edmans, Professor of Finance at London Business School.

Research and sources mentioned: James Surowiecki; Amy Cuddy; Robert Novy-Marx; Henk Bessembinder; McLean and Pontiff; Kent Daniel and Toby Moskowitz; Jonathan Berk and Richard Green; and research on football results, weather and markets, workplace culture, stock-return distributions, and post-publication anomaly performance. The discussion also refers to Warren Buffett, Charlie Munger, Julian Robertson, and David Booth.