Irrational Exuberance

A situation in which news of price increases spurs investor enthusiasm, which spreads by psychological contagion from person to person, in the process amplifying stories that might justify the price increases and bringing in a larger and larger class of investors, who, despite doubts about the real value of an investment, are drawn to it partly through envy of others' successes and partly through a gambler's excitement.

A situation in which news of price increases spurs investor enthusiasm, which spreads by psychological contagion from person to person, in the process amplifying stories that might justify the price increases and bringing in a larger and larger class of investors, who, despite doubts about the real value of an investment, are drawn to it partly through envy of others' successes and partly through a gambler's excitement. Feedback loop mechanism. Speculative bubbles are driven by a self-reinforcing cycle of investor enthusiasm and price increases. This process typically begins with a precipitating factor, such as technological innovation or economic policy changes, which sparks initial price increases. As prices rise, more investors are drawn in, fueled by: Fear of missing out (FOMO) Envy of others' perceived success Overconfidence in their ability to time the market Belief in "new era" narratives justifying high valuations Historical examples. This pattern has repeated throughout history in various markets: 1720s: South Sea Bubble (UK) and Mississippi Bubble (France) 1920s: U.S. stock market boom leading to the 1929 crash 1990s: Dot-com bubble 2000s: U.S. housing bubble Psychological factors. Irrational exuberance is sustained by cognitive biases and emotional responses: Confirmation bias: Seeking information that supports existing beliefs Herding behavior: Following the crowd Recency bias: Overweighting recent events and trends Overconfidence: Underestimating risks and overestimating abilities

People are ready to believe the majority view or to believe authorities even when they plainly contradict matter-of-fact judgment. Cognitive anchors. Investors often rely on mental shortcuts and reference points when making decisions, even if these anchors are arbitrary or irrational. Key psychological anchors include: Recent price levels Round numbers (e.g., Dow 10,000) Historical averages Expert predictions and price targets These anchors can lead to persistent mispricing and market inefficiencies. Social influence. Market behavior is heavily shaped by social dynamics and information cascades. Investors are influenced by: Word-of-mouth communication Social proof (following the actions of others) Authority figures and perceived experts Cultural narratives and popular sentiment The combined effect of these psychological and social factors can create powerful market momentum, driving prices far from fundamental values for extended periods.

The news media are in constant competition to capture the public attention they need to survive. Attention-grabbing narratives. The media plays a crucial role in shaping market sentiment by: Amplifying and spreading market-related stories Creating and reinforcing narratives…