An asset's price is ultimately determined by what someone is willing to pay, making the market a game of predicting collective human emotion, much like trading baseball cards. Even fundamentally sound assets can crash if sentiment turns negative, meaning investors are gambling on the emotional state of others.
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A stock's price consists of two parts: its fundamental operating value (profits), the "beer," and market speculation (emotion, hype), the "foam." Great investors like Warren Buffett aim to buy stocks for the price of the beer, not the foam, by identifying well-run companies at a fair price.
Post-mortems of bad investments reveal the cause is never a calculation error but always a psychological bias or emotional trap. Sequoia catalogs ~40 of these, including failing to separate the emotional 'thrill of the chase' from the clinical, objective assessment required for sound decision-making.
Unlike physical sciences where observation doesn't change the subject, the stock market's behavior is influenced by participants watching it. A market can rise simply because it has been rising, creating momentum loops. This "self-awareness" means price and value are not independent variables, a key distinction from more rigid scientific models.
The primary driver of market fluctuations is the dramatic shift in attitudes toward risk. In good times, investors become risk-tolerant and chase gains ('Risk is my friend'). In bad times, risk aversion dominates ('Get me out at any price'). This emotional pendulum causes security prices to fluctuate far more than their underlying intrinsic values.
Financial history rhymes because the underlying driver—human nature—is constant. Core desires for wealth, recognition, and love, along with the fear of pain and envy of others' success, have remained unchanged for millennia. These emotions will continue to fuel bubbles and crashes, regardless of new technologies or financial instruments.
The fathers of physics and biology both lost their fortunes in financial speculation—Newton in the South Sea Bubble and Darwin in railways. This demonstrates that intellectual brilliance in one domain does not translate to financial markets, which are governed by psychology and mercurial forces.
Media outlets are incentivized to generate clicks through hype and fear. This creates a distorted view of the market, causing retail investors to panic-sell during downturns and FOMO-buy during bubbles. The reality is usually somewhere in the less-exciting middle.
Based on Daniel Kahneman's Prospect Theory, once investors feel they are losing money, their behavior inverts. Instead of cutting losses, they adopt a "double or nothing" mentality, chasing high-risk gambles to escape the psychological pain of loss.
The stock price and the narrative around a company are tightly linked, creating wild oscillations. Investors mistakenly equate a rising stock with a great company. In reality, the intrinsic value of a great business rises gradually and steadily, while the stock price swings dramatically above and below this line based on shifting market sentiment.
The expectation that universal, instant access to information would lead to more efficient markets has been proven wrong. Instead, it has amplified sentiment-driven volatility. Stock prices have become less tethered to fundamentals as information is interpreted through the lens of crowd psychology, not rational analysis.
