100 Year Dow Chart with 25-Year Moving Average
Note: For a more up-to-date version of the above chart see 2010 Year-end Stock Market Update.
Above is a very long-term chart of the Dow, including the 25-year moving average (click chart to expand); it uses this past month's close for this year's close. It shows that the market rarely falls very far below its 25-year moving average.