If you try to move into low risk/low return investments when markets decline, and then move back into higher risk/higher return investments when markets rally, you could actually underperform compared with an investor who stays fully invested and rides out the ups and downs in a well-diversified portfolio of high quality stocks and bonds.
There are several reasons for this:
-
You could sell out after the market decline begins, and perhaps even after the market decline is almost over. In this case you will be selling low, not high. This locks in your loss.
-
Your costs will be higher than those of long-term investors. You will incur transaction costs and pay commissions every time you sell out or buy back into the markets.
-
You could miss the initial stages of the next market rally – while you wait to be sure that a recent uptrend is real and will be sustained.
Mistiming the market's highs and lows could seriously impact your investment returns.
It is
time in the markets - not timing the markets - that gives you the best chance of investment success.

Chart above: The return of the S&P 500 over this 20-year period, assuming that you remained fully invested through the market’s ups and downs, was $478,171. If you compare this return to the result when some of the market’s best days are removed from the calculation, something striking appears. If you missed only the 25
best days during this period, your return for the whole 20 years falls to $120,230.