This is a list of the largest daily changes in the Dow Jones Industrial Average.
List of largest daily changes in the Dow Jones Industrial Average Wikipedia
Some sources (including the file Highlights/Lowlights of The Dow on the Dow Jones website) show a loss of −24.39% (from 71.42 to 54.00) on December 12, 1914, placing that day atop the list of largest percentage losses. The New York Stock Exchange reopened that day following a nearly four-and-a-half-month closure since July 30, 1914, and the Dow in fact rose several percent that day (from 71.42 to 74.56, or +4.4%). However, the apparent decline was due to a later 1916 revision of the Dow Jones Industrial Average, which retroactively adjusted the values following the closure but not those before, and it represents the only discontinuity in the index’s history rather than an actual loss.
A point swing is the difference between the intraday high and the intraday low. (The intraday high may not be the same as the opening price; for instance, in the 2010 Flash Crash, the market reached an intraday high higher than the opening price).
This is distinguished from an intraday point drop or gain, which is the difference between the opening price and the intraday low or high.
This table shows the largest intraday point swings since 1987. As the "Net Change" column shows, 15 of these 20 largest intraday swings occurred during days on which the Dow declined, while only 5 occurred during days on which it advanced. Eight of the ten largest intraday swings occurred amidst the global financial crisis of 2007-08, and none of the top 20 occurred before the year 2000. At the time during the height of the crisis, nine of the ten largest intraday swings ever (and 13 of the top 20) occurred over a single span of trading days between September 29, 2008, and December 1, 2008.