The best stock. The best fund. The best ETF. 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 soared hundreds or thousands of percent 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
In the case of determining the best-performing market for stocks, it's 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.

And 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 what 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 really 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 as well. 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 monsters like Apple (NASDAQ:AAPL), up 725% over the past three years, or Hansen Natural (NASDAQ:HANS), up 680% the past 24 months. Even Daktronics (NASDAQ:DAKT) or Celgene (NASDAQ:CELG) -- both posting in excess of 50% compound growth over the past five 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 slow growth in the U.S. are booming internationally. For example, oil and gas producer PetroChina (NYSE:PTR) and metals and mining company CVRD (NYSE:RIO) have both returned in excess of 40% annually over the past thee years. These are stable, multibillion-dollar corporations. And companies such as America Movil (NYSE:AMX) are dominating fertile, untapped markets that are more saturated in the United States. The Mexican wireless service provider turned in a 56% return last year. And 68% in 2005. And 86% in 2004.

The best is yet to come
Certainly, looking at past performance of markets is an incomplete picture, and no one can accurately predict what the top market will be this year. But there is one prediction I'll go out on a limb to 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.

But 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.

The service also includes country profiles, a knowledgeable community, and a host of resources that help explain all the currency trickery. All of it is accessible with a free 30-day trial by clicking here. If after a test run you aren't convinced 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.

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. The Motley Fool has a disclosure policy.