Look, it's not that "emerging markets" is a loaded term. In fact, it's a pretty exciting one. You're talking about countries that are transforming themselves in a few short years from being highly dependent on their ability to sell raw materials to the West into dynamic, information-driven economies with burgeoning middle classes and plenty of domestic consumption.

Yes, they're emerging. But that sounds a bit like a butterfly emerging from a chrysalis. This is different. These countries are blowing up. We're not talking banana republics anymore. We're talking -- with apologies to Costa Rican President Oscar Arias Sanchez -- "Apple republics."

America's last growth frontiers
If you look at the performance of indexes tracking some of the biggest emerging markets, you'll see shapes ranging from mountain-climbing to parabolas to moon launches. China, Brazil, India, Argentina, Vietnam, and Mexico have all seen their stocks markets double, triple, or more in the past three years.

That's not to say this kind of growth will never happen again on the U.S. markets -- oh, all right, yes it is. This is the kind of growth rate that will never, ever happen again in the United States. It can't happen.

Our economy is too developed for the kind of explosive growth taking place in much of the developing world. We have no more great frontiers. Orlando and Las Vegas may well be the last U.S. cities to grow into metropolises. We're just not going to found a new great American city in the middle of Kansas.

How's that for a sobering thought? America's growth timeline bookends with Benjamin Franklin on one end and Wynn Resorts (NASDAQ:WYNN) and Disney (NYSE:DIS) on the other.

A new Houston every month ... please take back your money
Meanwhile, China is on the move. Not in the way you think, with its ever-expanding external influence. No, China has 200 million people living comfortably and another 1.1 billion who aren't but would like to be. The result is the greatest migration in the history of humankind. Each month, the major Chinese cities receive enough new inhabitants that they need to build the equivalent of Houston -- infrastructure and all -- to handle them.

India's economy has heated up to the point where the government is trying to build stronger restrictions against foreign money pouring in to invest in the country. Yes, on a per-capita basis, India is poor. But by the same measure, they're turning money away at the borders. Even countries you don't think of immediately, like Vietnam, Argentina, and Malaysia, are enjoying staggering growth rates.

Expensive -- yet dirt cheap
Obviously, you'd like to get involved with markets like these before they take off, so unless you've invested in them already, you've missed some enormous gains. But let me make three points: one historical, one prospective, and one differential.

Point 1
The historical one is this: In 1980, the Dow Jones Industrial Average stood below 1,000, the U.S. economy was in the tank, and the place that would soon be known as Silicon Valley was reeling from the loss of defense-industry jobs.

By the start of 1987, Intel (NASDAQ:INTC) was set to dramatically transform Santa Clara County, the Dow was ready to cross 2,000 after a 30% one-year rise, and Microsoft (NASDAQ:MSFT) had also had its IPO and had begun its long march to supercorporation following its fortuitous deal with IBM (NYSE:IBM).

In hindsight, was 1987 a bad time to invest? Heck, no, for the very reason that the American economy was still at the beginning of a great transformation. The big fortunes were still ahead. Sell in 1987, and you're kicking yourself for the next 20 years ... and counting.

Point 2
By this same measure, the transformation ongoing in emerging markets worldwide is still in its infancy. It's going to continue -- in fits and spurts -- for decades. The growth prospects in China are still virtually limitless.

This is why companies like Ctrip.com (NASDAQ:CTRP), even if they are expensive by nearly any operational measure, are ownable. It's why a well-capitalized Brazilian bank like Banco Itau (NYSE:ITU) trades at ratios well above comparably sized American banks. The United States grew at 2.1% annually the past five years. Argentina, Brazil, Chile? 4.6%, 3.2%, and 4.3%, respectively, with greater upside as Latin American economies solve some regulatory issues.

The calculus is pretty simple.

Point 3
And finally, the differentiation. While China and India have enjoyed salubrious rises in their share prices, they started at an extremely low base. Many people shun emerging-market investing because of the risks, the lower level of regulation, or the lack of protection. And they're right to be concerned. But things are improving in every country that has companies coveting Western capital, with the possible exception of Russia.

China's markets aren't as orderly as the Nasdaq, but they're not the wild West anymore, either. The differentiating point is this: Some of the countries with the highest level of shareholder protection, like Chile, Poland, and Taiwan, have seen their stock markets trail those of other similar markets. If you're worried about global share overvalue, it makes some sense to look into these kinds of markets.

In fact, it's what I do every day
I'd be remiss if I didn't point out that The Motley Fool has a service, Global Gains, that focuses solely on foreign stocks that can be bought directly on U.S.-based exchanges. The service is a year old, so while it's too early to draw too many conclusions, our foreign recommendations have trounced the markets, two of them doubling.

We live and breathe foreign stocks, and in two weeks we're heading to South America to search for more opportunities. If you'd like to receive our updates and research in real time from the field, simply provide your email address in the field below.