The anatomy of a bubble
Economist Hyman Minsky described a classic bubble in five stages. It starts with a displacement — a new technology, policy change, or economic shift that creates genuine opportunity. Smart money flows in during the boom. As prices rise, more investors pile in during the euphoria phase, convinced they can't lose. Eventually the market reaches distress as insiders begin selling. Finally, revulsion sets in and the crash arrives.
Famous bubbles through history
| Bubble | Asset | Peak-to-trough fall |
|---|---|---|
| Tulip Mania (1637) | Dutch tulip bulbs | ~99% |
| South Sea Bubble (1720) | South Sea Company shares | ~85% |
| Dot-com bubble (2000) | Tech stocks (NASDAQ) | −78% |
| US housing bubble (2006) | Residential property | −33% nationally |
| Crypto bubble (2021) | Bitcoin, altcoins | Bitcoin −77% |
Why bubbles form despite rational individuals
The paradox of bubbles is that individually rational behaviour creates collectively irrational outcomes. If prices are rising rapidly, it can be rational to buy — as long as you believe you can sell before the crash. This "greater fool" logic sustains bubbles even when every participant knows prices are stretched. Easy credit amplifies the effect: when borrowing is cheap, people take on leverage to speculate, which drives prices even higher.
Why you can't reliably short a bubble
Knowing a bubble exists doesn't make it easy to profit from its collapse. John Maynard Keynes famously observed that markets can remain irrational longer than you can remain solvent. Short-sellers who correctly identified the dot-com bubble in 1998 were wiped out waiting for it to pop — it took another two years. Michael Burry correctly identified the housing bubble, but nearly lost his fund to redemptions before it collapsed.
"When the music stops, in terms of liquidity, things will get complicated. But as long as the music is playing, you've got to get up and dance." — Chuck Prince, Citigroup CEO, 2007
What this means for you
The best defence against a bubble is a rules-based approach: regular rebalancing keeps you from becoming overweight in whatever is surging. When an asset class has dramatically outperformed over several years, trim it back to your target allocation — you don't have to call the top precisely to benefit from not being too exposed when it pops.