Don't you invest in that just because you think it's a good idea. I'm warning you.

Across 10 asset classes, over a near-40-year time horizon, and in increments of three, five, and 10 years, there's one investment vehicle that made for a total loser -- a dud.

It's gold -- that so-called safe haven for your assets -- and if you're considering it today, let me explain why you need to bypass it and move on. Although gold may well be one of your favorite items in the vault, as a long-term investment, it is just plain lousy.

Bring on the hate mail
You needn't take my word for it -- Investor's Business Daily pulled the data from a study conducted by two Merrill Lynch strategists. And today, very few have the gumption to say that gold is simply not worth your time. Why?

Perhaps because, as IBD wrote, "in one recent five-year period -- the one ended Feb. 7 -- [gold funds] leave a different impression. Gold funds tracked by Lipper Inc. cranked out an average annual return of 25.45% vs. U.S. diversified stock funds' 12.60%."

You can bet your bottom dollar those returns have a lot to do with the metal's relatively recent surge in popularity. As usual, investors continue to chase performance and follow the herd. But proponents will tell you there are more reasons to believe that gold is a worthwhile spot for your money these days.

With all the chaos in the marketplace right now and the impending threat of economic doom, the investing herd is thinking, "Hey, gold is the perfect option to safeguard money from hyper-inflation and make a good return at the same time." And though I agree that gold funds and industry giants such as Goldcorp can get hot at times, four decades' worth of data demonstrate that gold is a riskier and lower-returning investment than pretty much any other.

Higher risk/lower reward
The two folks at Merrill hit the nail right on the head when they said, "Investors often lose sight of longer-term historical investment results, especially during short-term periods of extreme volatility and trending markets."

Bingo!

Short-term, return-chasing thinking is precisely what is driving otherwise crafty investors toward bad decision-making, and that is exactly why you should be looking elsewhere right now. Before I get to where exactly, it is important to understand just what the gold bulls are thinking.

Looking through the other side
Supporters of gold like to note that the past 40 years were an unprecedented period of growth in the American economy. We witnessed the rise of the quintessential American business -- names like Southwest Airlines (NYSE: LUV), Starbucks (Nasdaq: SBUX), and other companies that revolutionized or invented their industries alongside booming growth in our domestic economy, the likes and returns of which we'll probably not experience again. And OK, this may be true.

Gold bulls go on to suggest that there is no reason to believe that the next 40 years of equity returns will look anything like the prior 40. Our economy is too big and too developed ... and that's probably true, too.

It's all about risk
According to Gold folk, we're entering an era of massive economic risk thanks to our miserable levels of national and personal debt. Sad to say, we now know this is true. Titans of our financial markets have dropped like a sack of potatoes in the past months, and now, even once-stodgy companies like Citibank (NYSE: C) and Bank of America (NYSE: BAC) could face the guillotine if just few a things don't go right. Hey, don't forget about political risk from terrorism, a more competitive China, and the end of cheap fuel. Risk is everywhere, isn't it?

To that I say: Where did the risk ever go?

Wasn’t it difficult for Americans to buy shares of Wal-Mart (NYSE: WMT) during the height of the Cold War and with the underlying threat of nuclear war? Yet investors who stuck with their guns on a stock as safe as Wal-Mart have since compounded an astounding 41.7% per year, compared to a measly 6.6% on gold since 1975.

With all the bear markets, through the oil crises, Black Monday, the implosion of the dot-coms, stagflation, and our current economic mess (pretty much all the economic risks you can think of), do you know which asset class failed to reward investors at rates comparable to all other asset types, while also exposing investors to a tremendous amount of volatility? Yup, our favorite precious metal: gold.

Goldfinger will not be pleased
I'm not bashing gold simply to bash. In fact, it isn't the worst idea to put a small slice of your portfolio in gold to diversify in case I'm wrong. But there's a better solution for the rest of your money: Go with the asset class that has consistently demonstrated the highest returns on investment with some of the lowest elements of risk -- small-cap stocks.

This isn't my own unproven theory -- the data comes from the same IBD study I mentioned before. Generally, equities trump just about every available investment alternative you have. But small caps in particular demonstrate significantly high returns with comparatively low risk. Plus, much of the negative information that we're hearing these days about our economy has already been priced into the markets or is getting priced in as we speak. Don't dwell on hindsight information -- look forward.

The truth will make you rich
To find the best of the small-cap world, you've got to think like a great small-cap stock. Remember: The giants of industry you know today once resembled the Netflixes (Nasdaq: NFLX) and the Blackboards (Nasdaq: BBBB) of the world we know now. And though our economy has matured, great companies will inevitably find their way to the top of the U.S. markets, displacing others if they have to.

That's because many of the world's best businesses -- like Netflix -- started small, with great ideas on top of cash-generating business models and entrepreneurial owners at the helm. And there are plenty more out there where those came from.

If you want to be on the side of returns that smash gold in the long run, then you must allocate toward these types of stocks.

Need some ideas? Consider our Motley Fool Hidden Gems small-cap service, where our team's picks have beaten the market by 15 percentage points on average. Click here to get all of our research and recommendations free for 30 days.

This article was first published March 3, 2008. It has been updated.

Fool analyst Nick Kapur used to have a gold class ring, but sadly, he lost it. Starbucks and Netflix are Stock Advisor recommendations. Wal-Mart is an Inside Value recommendation. Blackboard is a Hidden Gems recommendation. The Motley Fool has a disclosure policy.