Here's why so many financial advisers say it's the only sensible strategy and urge you not to yank your money out of the market when it's going down and buy when it's going up.

According to Ibbotson Associates, savers who bought $10,000 worth of stocks in January 1980 would have had $286,000 by December 2006 if their investment simply tracked the Standard & Poor's 500 Index and the money was in the market the entire time.

But if they missed the markets' five best days during that time, the account would total only $212,000 -- or $74,000 less.

Missing the best 10 days would have cut the balance to $131,000. Missing the best 30 days would have resulted in only $78,000.

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