Irrational Exuberance

In an essay in the Wall Street Journal, Stephen Greenspan explains some of the psychology behind the success of Ponzi schemes: Why We Keep Falling For Financial Scams.

The basic mechanism explaining the success of Ponzi schemes is the tendency of humans to model their actions — especially when dealing with matters they don’t fully understand — on the behavior of other humans. This mechanism has been termed “irrational exuberance,” a phrase often attributed to former Federal Reserve chairman Alan Greenspan (no relation), but actually coined by another economist, Robert J. Shiller, who later wrote a book with that title. Mr. Shiller employs a social psychological explanation that he terms the “feedback loop theory of investor bubbles.” Simply stated, the fact that so many people seem to be making big profits on the investment, and telling others about their good fortune, makes the investment seem safe and too good to pass up.

In Mr. Shiller’s view, all investment crazes, even ones that are not fraudulent, can be explained by this theory. Two modern examples of that phenomenon are the Japanese real-estate bubble of the 1980s and the American dot-com bubble of the 1990s. Two 18th-century predecessors were the Mississippi Mania in France and the South Sea Bubble in England (so much for the idea of human progress).

Mr. Greenspan has model of four explanatory factors for “foolish action.”

  • situation – a social challenge you need to solve
  • cognition – a deficiency in knowledge and/or clear thinking
  • personality – trust and niceness
  • emotion – greed or the desire to not lose

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