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Market Bubbles & Crashes - Behavioral Explanation

Definition of Bubbles

Bubble: Asset prices rise far above fundamental value, then crash.

Characteristics:

  • Rapid price appreciation (100%+ in 1-2 years)
  • Disconnect from fundamentals
  • "This time is different" narrative
  • Widespread participation
  • Eventual collapse

Famous Bubbles

Tulip Mania (1637): Bulbs cost more than houses → Crashed 99%

South Sea Bubble (1720): Stock rose 10x in months → Crashed 90%

1929 Stock Market: Rose 400% in 5 years → Crashed 89%

Dotcom (2000): Nasdaq 5x in 3 years → Fell 78%

Housing (2008): "Housing never falls nationally" → 40% crash

Crypto (2017): Bitcoin $20K → $3K (-85%)

Behavioral Causes

Overconfidence: "I know this will keep rising"

Herding: "Everyone's buying, must be good"

Availability Bias: Recent gains seem representative

Anchoring: New highs become reference, pull prices up

Feedback Loops: Price rises attract buyers → Prices rise more

Stages of Bubbles (Minsky Model)

Displacement: New opportunity (internet, housing)

Boom: Prices rise, attract attention

Euphoria: "This time is different!" rhetoric

Profit-Taking: Smart money exits

Panic: Rush for exits, liquidity vanishes, crash

Why Rational Arbitrage Fails

Limits to Arbitrage:

  • Can't short enough (constraints)
  • Timing uncertain ("markets can stay irrational longer than you can stay solvent")
  • Career risk (fired if early)

Example: During 2000 bubble, rational managers shorting tech lost clients, were forced to cover. Bubble lasted 2 more years before collapsing.


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