My money, I should add, is where my mouth is: What I advise here is essentially identical to certain instructions I've laid out in my will. One bequest provides that cash will be delivered to a trustee for my wife's benefit. (I have to use cash for individual bequests, because all of my Berkshire Hathaway (BRKA) shares will be fully distributed to certain philanthropic organizations over the 10 years following the closing of my estate.) My advice to the trustee could not be more simple: Put 10% of the cash in short-term government bonds and 90% in a very low-cost S&P 500 index fund. (I suggest Vanguard's. (VFINX)) I believe the trust's long-term results from this policy will be superior to those attained by most investors -- whether pension funds, institutions, or individuals -- who employ high-fee managers.
I have good news for these nonprofessionals: The typical investor doesn't need this skill. In aggregate, American business has done wonderfully over time and will continue to do so (though, most assuredly, in unpredictable fits and starts). In the 20th century, the Dow Jones industrial index advanced from 66 to 11,497, paying a rising stream of dividends to boot. The 21st century will witness further gains, almost certain to be substantial. The goal of the nonprofessional should not be to pick winners -- neither he nor his "helpers" can do that -- but should rather be to own a cross section of businesses that in aggregate are bound to do well. A low-cost S&P 500 index fund will achieve this goal.
That's the "what" of investing for the nonprofessional. The "when" is also important. The main danger is that the timid or beginning investor will enter the market at a time of extreme exuberance and then become disillusioned when paper losses occur. (Remember the late Barton Biggs's observation: "A bull market is like sex. It feels best just before it ends.") The antidote to that kind of mistiming is for an investor to accumulate shares over a long period and never sell when the news is bad and stocks are well off their highs. Following those rules, the "know-nothing" investor who both diversifies and keeps his costs minimal is virtually certain to get satisfactory results. Indeed, the unsophisticated investor who is realistic about his shortcomings is likely to obtain better long-term results than the knowledgeable professional who is blind to even a single weakness.