Per the below linked WSJ article:
* A common definition of a market 'Crash' is a 20% decline in a single day or span of several days. For some perspective, the Dow's crash in 1987 was a 22.6% correction in one day. The 1929 crash was punctuated by back-to-back declines of 12.8% and 11.7%.
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* The Dow Jones Industrial Average index is Down 39% since hitting a record of 14,164.53 one year ago...The Dow's recent 7 day decline of 21% is the largest seven-session percentage drop since the 1987 crash. During the 1987 crash, the Dow Jones lost 43% over seven days.
* At Thursday's close, the Price To Earnings Ratio (P/E Ratio) of the S+P 500 was down to 10.7, the Lowest since the Early 1980's (hopefully those 2007/08 earnings won't turn out to be 'peak year' earnings)...the market's historical P/E Ratio is 15
http://online.wsj.com/article/SB122359593027021243.html
Data Courtesy: The Wall Street Journal