It's a question that has been on many investors' minds since the stock market hit the skids two weeks ago: should portfolios be rejigged in light of rising market volatility?
On the one hand, the current sell-off, prompted by fears over a credit crunch stemming from troubles in the mortgage market, has already shaved around 800 points off the Dow Jones industrial average. And history has shown that whenever stocks start to have major one-day swings after a prolonged period of calm, it is typically a sign that "we've opened Pandora's box of volatility", said Sam Stovall, chief investment strategist at Standard & Poor's.
On the other hand, this is the fourth spike in stockmarket volatility in a little more than a year - the last one began at the end of February. In the three previous cases, the market's roller-coaster ride, while frightening, proved rather short. So this might not be the best time to drastically overhaul your asset allocation strategy by reducing your exposure to stocks.
But when it comes to managing your portfolio, you don't have to make major long-term adjustments to your mix of stocks and bonds to dampen the gyrations in your investments. Sometimes, all it takes is a periodic rebalancing of your portfolio, back to your desired mix of stocks and fixed-income investments, to smooth out the bumps.
To be sure, making a major and permanent shift to a much more conservative asset allocation strategy can make a real difference in your overall risk profile.
For instance, over the last half-century, the worst one-year stretch for an American investor's portfolio of 60 per cent stocks, 30 per cent bonds and 10 per cent cash investments was a loss of 24.1 per cent. That occurred in the 12 months that ended in September 1974.
By comparison, the worst one-year loss for a more conservative US mix - 40 per cent stocks, 40 per cent bonds and 20 per cent cash - was just 15.5 per cent during the same period.
Yet to achieve this lower risk, you would have to give up a decent amount of gains. In this case, the switch in asset allocation strategy would have reduced your average annual returns to 8.3 per cent from 9.2 per cent.
For some investors, that may be too significant a loss of potential returns to consider.
So the asset manager T. Rowe Price recently posed a different question. Can you significantly reduce your exposure to risk simply by rebalancing your portfolio once a year, rather than permanently reducing your exposure to stocks for the long run?
The answer turns out to be yes.
Say you started investing at the end of 1984, in a portfolio consisting of 60 per cent stocks, 30 per cent bonds and 10 per cent cash. And further assume that you never rebalanced this portfolio back to that 60-30-10 ratio. Instead, you did what a surprisingly large percentage of individual investors do: you let the market take your investments for a ride.
By the end of June, this strategy would have earned an average annual gain of 11.1 per cent since 1984. Now, had you started in 1984 with the same strategy, but this time rebalanced your portfolio annually, you would have earned nearly as much on your investments: 10.7 per cent a year, on average.
But at the same time, that portfolio would have been 18 per cent less volatile, based on standard deviation, according to T. Rowe Price. The buffering effect of rebalancing might have been enough to let you sleep better at night.
Unfortunately, a vast majority of individual investors fail to take that simple step. Only 18 per cent of workers who invested in a retirement plan rebalanced their portfolios last year, a study by the employee benefit research firm Hewitt Associates, shows.
The fact is, whether or not you tweak your mix of stocks and bonds, the market will do it for you - though maybe in a way you won't like. Over the long term, stocks tend to outperform bonds. So "if you rely on inertia and don't rebalance regularly, over the long run, you're going to end up with a bigger allocation to stocks than you started with", said Christine Fahlund, a senior financial planner at T. Rowe Price in Baltimore.
But rebalancing is not just about resetting your mix of stocks and bonds. You should also consider periodically resetting the types of stocks you own.
For instance, Mr Stovall notes that over the last five years, many of the best-performing areas of the stockmarket have also been among the most volatile.
Those include the basic materials, telecommunications and technology sectors, all of which have a "beta" of more than 1.0. (Beta measures the tendency of an investment to go up or down, relative to the market - in this case the S.& P. 500-stock index. So a beta of more than 1 implies that if the S.& P. 500 were to rise or fall 5 per cent, for example, that investment would rise or fall even further.)
On the other hand, two of the lowest beta sectors in the market - health care stocks, with a beta of 0.6, and consumer staples stocks, at 0.5 - have been the market's worst performers over the past five years.
One way that investors might consider rebalancing the stock portion of their portfolios is to "gravitate toward areas with lower volatility, like health care and consumer staples, while avoiding those highly volatile areas that have already done exceptionally well," Mr Stovall said.
Jeffrey Kleintop, chief market strategist at LPL Financial Services in Boston, said that another way to rebalance - without selling any holdings - is simply to take your new money and invest it in areas that many investors have ignored in recent years, like large-capitalisation domestic growth stocks and stock funds. These may be worth buying now.
While many people associate large-cap growth stocks with technology, these equities can also be found in the health care and industrial sectors, both of which have a beta of less than 1.
The notion of buying stocks amid a market storm may seem unappetising. And some investors may decide simply to wait to see whether this is a short-term sell-off or the start of a real correction.
But keep in mind that if you have not rebalanced your portfolio for several years, chances are that you probably have more equity exposure than you intend. Moreover, you are probably overexposed to the most volatile types of stocks. So some rebalancing may be better than no action at all.