The best stock. The best fund. The best exchange-traded fund. As investors, we're constantly on the lookout for the best opportunities.

Just as we salivate to crown the year's best-dressed celebrity or the best pizza in Manhattan, we drool over charts and tables of stocks that surged hundreds or thousands of percentage points in a year. That way, we can dream about how we'd feel if we had spotted the stock and bought before the run-up, and then get jumpy about finding the stock that will repeat or beat that performance in the coming year.

But rather than just looking at the story of one or a few individual stocks that soared last year, investors can learn more by looking at markets in general for the lessons they teach.

The best of 2006
Determining the best-performing market for stocks is a little tricky. Comparing world markets involves adjusting for currency fluctuations and inflation, which is never straightforward.

Thankfully, the Motley Fool Global Gains team has developed a model to compare world markets on an even basis to determine which markets are growing and which are declining in value. With a common reference, yearly and monthly comparisons help investors see just what regions of the world are flourishing or decaying.

What they found was amazing. Surprisingly, the United States doesn't even crack the top 10 for 2006. Neither do many other advanced, industrial nations we commonly equate with economic growth. So, which international stock exchange actually tops the list?

(Opening envelope ...)

Zimbabwe. Yes, you read correctly. Zimbabwe's market returned a stunning 912% in 2006 -- a single year. But is this real? Can investors actually realize this kind of gain?

This is where the tricky part comes in. The dramatic return of Zimbabwe's exchange is partly the product of a restricted currency value in the face of hyperinflation. The inflation and currency chaos have also been behind extended periods of negative returns in the Zimbabwe market. So, no, investors shouldn't expect Zimbabwe (or any other stock exchange, for that matter) to deliver achievable organic growth at this level for any lengthy period of time.

But even beyond the near chaos of gyrating frontier markets, other more stable markets are booming. No. 2 and No. 3 on the Global Gains list, Venezuela and China, more than doubled in the year, up 156% and 130%, respectively, and some of these regions have grown at extremely high rates for years.

For the U.S. markets to grow at rates this high, you'd have to see hundreds of high-growth success stories such as the recent winners like Crocs (NASDAQ:CROX) and credit card master MasterCard (NYSE:MA), both up more than 260% in past 12 months. Even Genzyme (NASDAQ:GENZ) and Gilead Sciences (NASDAQ:GILD) -- posting 17% and 36% compound annual growth, respectively, over the past 10 years -- are too rare in the United States. Much of the U.S. market is made up of slower-growing or cyclical industries.

But many of the industries that show mature growth in the U.S. are booming internationally. For example, Chinese wireless service provider China Unicom (NYSE:CHU) and telecom firm China Telecom (NYSE:CHA) have returned 37% and 25% annually, respectively, over the past three years. These are large, multibillion-dollar corporations tapping new regions of growth, and companies such as Brazilian supermarket and department store operator Companhia Brasileira de Distribuicao (NYSE:CBD) benefit from growing economies in sectors that are more saturated in the United States. The stock has gained 140% in the past three years.

The best is yet to come
Certainly, looking at past performance of markets provides an incomplete picture, and no one can accurately predict what the top market will be this year. However, there is one prediction I'll go out on a limb and make -- the United States will not be the top market of 2007. If it is, I'll eat a pair of dirty socks.

The reason I'm comfortable facing such a sweaty encounter is that the odds are heavily in my favor -- international stock markets contain solid yet little-known companies that are pursuing largely undeveloped and untapped markets. All this is the recipe for dramatic growth -- growth that investors would be imprudent to ignore.

That said, dramatic growth also comes with considerable risk, so tread cautiously. Or join us at the Global Gains international investing service, which was created to help investors leap from simple geographic knowledge to understanding international market dynamics. Global guru Bill Mann and his team of analysts scour the world for the best international companies with solid management and transparent finances for your consideration.

In fact, Bill recently returned from a research trip to India, China, and Taiwan. You can read all of his updates and research from that trip by clicking here and joining Global Gains free for 30 days. If after a test run you aren't convinced that the best market of 2007 is international, save a pair of your best socks -- we'll see who's chewing on soiled cotton come year's end.

This article was originally published on Feb. 14, 2007. It has been updated.

Fool contributor Dave Mock doesn't sweat -- he glistens. He owns no shares of companies mentioned here. The longtime Fool is also the author of The Qualcomm Equation. MasterCard is an Inside Value recommendation. The Motley Fool has a disclosure policy.