The false belief in 2000 was disabused when the Nasdaq 100 Index fell 80% in just 30 months and the majority of the most popular dotcom stocks went to zero.

A “mania,” on the other hand, is defined as excessive enthusiasm. I would take it a step further and suggest that a mania in the financial markets is marked by excessive enthusiasm that leads to belief in the impossible that allows for a bubble to form.

How The U.S. Stock Market May Be ‘Turning Japanese’

NIKK in 1989