The "Couch Potato" portfolio is one of those too-good-to-be-true investment plans, like buying only growth stocks, or following the recommendations of a newsletter writer or astrologer, or buying stocks only in months that contain an "R."

The difference is that the Couch Potato, more than a decade old now, seems to do all the right things.

It is understandable and easy to put together. Its returns regularly are higher than what you could get from most comparable mutual funds. It doesn't cost much.

Indeed, the hardest part of the Couch Potato may be self-discipline: Putting it together and then leaving it alone, despite what the market is doing or what the pundits are saying.

Here's how to build a Couch Potato portfolio: Invest half of your money in the Vanguard 500 Index fund. Invest the other half in the Vanguard Total Bond Market fund. Step back and forget about it until this time next year.

"The basic notion is that you have a sure shot at beating 70 to 75 percent [of the] professional managers simply by lowering expenses," says Scott Burns, the Dallas journalist who thought up the Couch Potato and has been championing it ever since.

The accompanying chart tells the story. The Couch Potato yielded a higher total return than balanced mutual funds in almost all of the last 11 years. The data, from Morningstar, include annual operating costs that are taken out of each shareholder's assets. (Expenses average 1.3 percent for the balanced funds, vs. 0.16 percent for the two Vanguard funds.)

The Couch Potato has other good points. A big one is that it stops you from making bad decisions. That includes impulse buying and panic selling — which are a lot more common than most people want to admit.

Another plus is that risk is relatively low, in part because diversification dampens the ups and downs of the market. It's also because you're not guessing — as actively managed mutual funds must do — what's going to be hot tomorrow or the next day.

There is one big drawback: These are index funds, which means that they are, by definition, average performers. The best managed mutual funds, or individual stocks for that matter, will blow them out of the water. You pay your money — 1.3 percent for those balanced funds — and you take your chances.

It is worth noting that the Vanguard Group has been subpoenaed in the ongoing mutual fund scandal stirred up by New York Attorney General Eliot Spitzer. Vanguard was not named in Spitzer's complaint, and there is so far nothing to indicate underhanded trading practices at Vanguard. But Spitzer has demanded to see information and documents.

On the other hand, Burns has suggested some alternatives to Vanguard. Schwab offers similar index funds, tracking the S&P 500 and the broad bond market.

And there are exchange-traded funds — second cousins to mutual funds that trade like stocks — that will do the job. On the bonds side, Burns named the iShares Lehman 7-10 Treasury Index.

One other note: Burns follows his own advice. "All the accounts I have control over are in index funds," he said. He is a little heavy in stocks, he added, to balance out other parts of his retirement package, including a pension and a 401(k) with limited choices.

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