Define: Greater Fool Theory

Belief held by one who makes a questionable investment, with the assumption that he/she will be able to sell it later to a bigger fool.

The greater fool theory says there’s always someone – an even greater fool – that will overpay for a stock that is already overpriced.

The greater fool theory may be used as a general investment strategy during an overheated bull market. More frequently, the greater fool theory applies to highly speculative equities, with ritzy names but few earnings. While cynical, the greater fool theory contains some truth: Money managers who, based on the fundamentals, ignore the greater fool theory and refuse to buy highly speculative stocks – like Japanese bank equities in the 1980s or Internet stocks in the 1990s – can cost their clients billions. As the greater fool theory predicted, for years there was always some “fool” who paid even more for these overpriced investments. The major problem with the greater fool theory is the enormous downside risk: At some point, despite the greater fool theory, no one will buy such an overpriced stock and its price collapses.

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This glossary post was last updated: 29th March 2024.