Fact: Despite huge growth in places like China and India, the U.S. stock market is still the world's largest.

But here's another fact: More than half of the world's stock value is outside of the ol' U.S. of A. That's thousands and thousands of companies, many of which are in places most of us don't often think about. But it's a safe bet that among those places and companies are some of the greatest investment opportunities of the next decade.

There's a lot of money to be made out there. Does your portfolio reflect that reality?

It's a great big world out there
Most of us have some global exposure in our portfolios, even if only indirectly, via American-based companies with a big global presence. Own Coca-Cola (NYSE: KO) or hold a fund that does? It's only the top-rated global brand, doing business just about everywhere there are thirsty people. Wal-Mart (NYSE: WMT) is already the world's largest retailer, and it's expanding rapidly in huge markets like China and India. Speaking of China, General Motors (which will be back in your index funds shortly) has an enormous presence in the Middle Kingdom, which is eclipsing the U.S. as the automaker's most important market (yes, really).

But it's one thing to hold a global giant, even a non-U.S. one like Finnish cell phone giant Nokia (NYSE: NOK), whose products are ubiquitous in many developing countries. It's another thing entirely, sometimes a much better thing, to hold a company or a fund that is tied to a particularly promising niche or region.

For instance, ever heard of Banco Latinoamericano de Comercio Exterior (NYSE: BLX), or "Bladex" for short? Bladex, headquartered in Panama, is a "trade bank," meaning a bank that makes short-term loans to facilitate international trade. Buying a bank stock might not seem like a good idea right now, at least from a U.S. perspective, but this one is a solid, conservatively run business that is poised to grow nicely as the Latin American economies recover and expand.

Or how about Mumbai-based automaker Tata Motors (NYSE: TTM)? Tata introduced its first passenger car in 1998, a small, inexpensive sedan perfectly suited to the just-starting-to-boom Indian market. It has ridden that success to become India's largest automaker, a big fish in a rapidly growing pond -- and has since begun to branch out overseas, buying venerable British brands Jaguar and Land Rover in 2008.

These two companies are regional heavyweights in markets poised for big growth. How can we find other opportunities like these? And more to the point for many investors, how can we take advantage of these opportunities in our retirement portfolios?

An important addition to your long-term portfolio
Getting more international exposure into your 401(k) or IRA isn't as simple as buying a single fund or ETF that covers the whole world outside of the U.S. For one thing, it's a big world out there! Different parts of the world are going to generate very different investment results. A more thoughtful approach is in order.

For instance, while Europe as a region has been fairly stagnant over the last year, the group of countries commonly called "emerging markets" -- China, India, Russia, Brazil, and so forth -- has posted some impressive numbers. One easy way to buy some of that growth is via the Vanguard Emerging Markets ETF (NYSE: VWO) or a similar fund. But the Vanguard fund is led by heavyweight telecom giant China Mobile (NYSE: CHL), and with median market caps around $17 billion, these aren't small-cap funds.

Diversification remains key
Is that a concern? It might be: As in other parts of your portfolio, diversification enhances your chances of long-term success. In an article in the latest issue of the Fool's Rule Your Retirement newsletter, advisor Robert Brokamp pointed out that lots of "international" funds are heavily tilted toward large-cap names, yet much of the growth in these markets comes from smaller-cap stocks.

Finding those kinds of smaller-cap stocks can be a challenge for many investors, and this is one of those asset classes where buying a fund makes sense for many. Robert did some research and identified several high-quality international funds with a smaller-cap focus, any of which would be a good way to add exposure to your retirement portfolio.

If you're thinking along those lines and would like a short-cut on the research, I encourage you to check out Robert's article. Rule Your Retirement is a paid service, but you can get full access right now with a no-obligation 30-day free trial. Just click here to get started.

Fool contributor John Rosevear owns shares of Vanguard Emerging Markets ETF. Coca-Cola, Nokia, and Wal-Mart are Motley Fool Inside Value recommendations. Bladex is a Motley Fool Global Gains choice. Coca-Cola is a Motley Fool Income Investor recommendation. The Fool owns shares of Bladex, Coca-Cola, Wal-Mart, China Mobile, and Vanguard Emerging Markets Stock ETF. You can try any (or all!) of our Foolish newsletter services free for 30 days, with absolutely no obligation.

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