What Diversification Can Do For You

During 2008, the principle of diversification failed to protect investors from losses as virtually all classes of investments lost money. So what does diversification do for an investor?

What Diversification Can Do for You
The first thing you should know is that it can't guarantee you the highest possible return. In fact, it guarantees you won't earn the highest possible return. By spreading your money around you assure that you will have at least some of your money in lagging investments, which will reduce your portfolio's potential return.
By the same token, diversification can't totally immunize you from losses. To do that, you would have to do the opposite of diversifying -- i.e., plow all your money into the most secure investments, such as Treasury bills or short-term bank CDs.
What diversification can do for you, though, is give you a shot at higher returns than you will get in the most secure investments while limiting your risk somewhat.
Notice I said "somewhat." Fact is, if you want the value of your money to grow more than it will in T-bills and the like, you've got to invest in asset classes that have the potential for higher long-term returns, such as stocks and bonds. But those higher returns come with more risk. In the investment world, that risk can take several forms, but generally the riskier an investment, the more volatile it is, the more its value will jump around from year to year.
You can't eliminate that risk. But by investing your money in a mix of secure and more volatile assets, you can reduce the potential downside in a given year. For example, if you'd had all your money in a diversified portfolio of U.S. stocks last year, you'd have lost just under 40%. If, on the other hand, you'd had 60% of your money in stocks, 30% in a broad bond index fund and 10% in cash last year, you would have lost roughly half that amount, or around 20%.(See editor's note.)
That kind of cushion is important for a couple of reasons. For one thing, it makes you less likely to panic in a bad year and sell off riskier investments with higher long-term return potential at what may be the worst possible time. A less volatile portfolio is also less likely to take a devastating hit that may be difficult to recover from. That's an especially important consideration when you're dealing with 401(k)s or other retirement accounts and you're nearing retirement age or are already retired and withdrawing money from such accounts.
So the key to getting the benefit of diversification is settling on a mix that's right for you.
Ideally, your mix should consist of assets that don't all move in sync with each other or, to put it in investing terms, that aren't too highly correlated with each other.
It's okay for gains in some investments to offset losses in others in some years. But on balance your gains should outweigh losses most years. And, while down years are inevitable with growth-oriented investments, whatever assets you're investing in should have a positive long-term return. Diversification isn't a magic formula that can turn recurring sizeable losses in your investments or your portfolio overall into long-term wealth.

What Diversification Can't Do for You
But as big an advocate as I am of diversifying among a variety of asset classes, I also feel that the concept has been stretched out of shape over the years, in some cases even beyond recognition.
Specifically, I think the benefits of diversifying have been oversold by some advisers who seem intent on making themselves come off like investment wizards capable of creating all-upside-no-downside portfolios. But I'm wary of these supposedly more sophisticated portfolios.
So I suggest keeping things simple. Start with a realistic sense of how much risk you can handle and then build a diversified portfolio of stocks, bonds and cash. If you want to get more fancy, you can throw in some foreign stock funds and maybe some REITs or real estate-related mutual funds. But don't go overboard. The more complicated your portfolio is and the more wide-flung your holdings, the more attention and care it will need.
Finally, remember that to get the full benefit of diversifying you ought to rebalance periodically to restore your portfolio to its proper proportions.
Of course, you can always take the other route you suggest and just buy CDs. But unless you have so much money that you can accumulate a large enough nest egg despite their low yields, I'm not sure that you can do this and also not worry.