Greenspan's comment was made during a televised speech on December 5, 1996 (emphasis added in excerpt): The
Tokyo market was open during the speech and immediately moved down sharply after this comment, closing off 3%. Markets around the world followed. Greenspan wrote in his 2008 book that the phrase occurred to him in the bathtub while he was writing a speech. The irony of the phrase and its aftermath lies in Greenspan's widely held reputation as the most artful practitioner of
Fedspeak, often known as Greenspeak, in the modern televised era. The speech coincided with the rise of dedicated financial TV channels around the world that would broadcast his comments live, such as
CNBC. Greenspan's idea was to obfuscate his true opinion in long complex sentences with obscure words so as to intentionally mute any strong market response. The phrase was also used by
Yale professor
Robert J. Shiller, who was reportedly Greenspan's source for the phrase. Shiller used it as the title of his book,
Irrational Exuberance, first published in 2000, where Shiller states: Shiller is associated with the
CAPE ratio and the
Case–Shiller Home Price Index popularized during the housing bubble of 2004–2007. He is frequently asked during interviews whether markets are irrationally exuberant as asset prices rise. There was some speculation for many years whether Greenspan borrowed the phrase from Shiller without attribution, although Shiller later wrote that he contributed "irrational" at a lunch with Greenspan before the speech but "exuberant" was a previous Greenspan term and it was Greenspan who coined the phrase and not a speech writer. ==Continued use==