Where are tomorrow's consumers? Not where you expect

As emerging market economies continue to raise incomes in the developing world, multinational consumer product companies are expanding their reach to far-flung markets.

And 25 years from now, they'll likely find the bulk of their new consumers in entirely new places.

The definition of "middle class" consumers varies widely, but economists generally peg the starting point at about $10 a day in per capita income. To date, the bulk of global consumer demand has been limited to the world's developed economies. But that is expected to shift dramatically in the coming decades.

Today, for example, Asia is home to less than a quarter of the world's middle-class households, according to a Brookings Institution study. By 2020, the researchers predict, that share could double.

"A large mass of Asian households have incomes today that position them just below the global middle-class threshold," according to the study. "So increasingly large numbers of Asians are expected to become middle class in the next 10 years."

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Consumer products companies will also likely find their next generation of customers living in one of the burgeoning "megacities" that are rapidly expanding around the globe. That's the result of a historic migration that is underway around the world, from the countryside to swelling urban centers.

One hundred years ago, just 2 out of 10 people on Earth were urban dwellers. Today more than half the world's population lives in cities, generating some 80 percent of global economic output. By the middle of this century, 7 out of 10 people will be living in urban centers, according to Hot Spots 2025, a report prepared by the Economist Intelligence Unit for Citibank.

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Many of those new arrivals will find a better life—with rising disposable incomes that will give them increased purchasing power. Today some three dozen cities around the world make the megacities list of having populations of more than 10 million, including Tokyo and Osaka in Japan; Chongqing, Shanghai and Beijing in China; Sao Paulo, New York, Mexico City; Mumbai and New Delhi in India; and Dhaka, Bangladesh, according to data compiled by Oxford Economics. By 2030 more than a dozen more will be added to the list.

Globalization also means the highest growth will come from megacities that aren't on many marketers' radar screens today As globalization allows cities to compete in key industries or services—from finance to technology—the growth in wealth and disposable income will also shift to unfamiliar locations.

By the middle of this century, for example, Wuhan in China is expected to generate more than 10 times the GDP growth of Auckland, New Zealand, according to a report by the McKinsey Global Institute.

For global consumer products companies, the rapid spread of mobile communications networks and the Internet are helping them identify and reach new customers among this emerging consumer class. In many countries, those new customers see iconic Western brands as a way of showing off their new spending power.

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American fast food purveyors, for example, are finding that people around the world are working up a voracious appetite as they embark on the upward journey to middle-class status. Households with rising incomes in the developing world are hungry for all-American exports like Footlongs, Big Macs and extra crispy chicken tenders.

That's helped revive sales for chains that have saturated markets in the developed world. Despite early signs that a fast food diet is no healthier in Beijing than it is in Boston, consumers who are new to middle-class dining seem less concerned about the health risks of the high-fat, high-sodium fare that many Americans now seek to avoid.

As wages in the U.S. and Europe expand at a tepid pace, household incomes in much of the developing world are leaping ahead. Over the next two decades, those gains are expected to introduce billions of new consumers to menus from fast food chains that are among some of the most iconic American brands.

Read MoreNew global middle class hungers for good ol' US fast food

And as many chains have saturated the U.S. market (and American tastes have shifted) the fast food industry is finding a hungry market in far-flung locations—from Malawi to Mongolia.

"A lot of domestic chains are completely refocusing their business on the international market," said IBISWorld Industry analyst Andy Brennan. "And most of them have been quite successful at it."

—By CNBC's John Schoen

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