In the 10 years ended Dec. 31, 2007, the Dow never once swung by more than 9% during the course of a trading day. So far in 2008, with less than eight weeks to go, there have been six such giant swings. Over the entire decade through the end of last year, the Dow bounced around by more than 5% in a single day a total of 14 times. So far this year, that has happened 20 times; what used to take place barely more than annually has occurred once every 11 trading days in 2008.
Sounds like a bubble to me.
Getting a Frazzled Mr. Market to Settle Down
The Wall Street Journal
November 8, 2008