Investors looking to cash in on the next big emerging-market story might have to go into Africa.

It’s been more than a decade since emerging markets came on U.S. investors’ radar screens in a big way when economist Jim O’Neill coined the acronym BRIC to describe the then-sleeping giants of Brazil, Russia, India and China.

Boy, did that turn out to be a good call. The BRICs were some of the hottest areas of growth and investment returns over the past 10 years.

But today? Not so much.

The mighty BRICs took a big hit from the global financial crisis and might never recover their torrid growth rates. Just consider how severe the slowdowns have been:

• Brazil, hampered by skyrocketing costs, inflation, consumer debt and sclerotic economic policy, is struggling to maintain any growth at all. Three years ago, gross domestic product was expanding at a 9% annualized rate. Today it’s waddling along at 1.4%.
• Russia, an oil oligarchy subject to the whims of the global energy market, had annualized GDP growth of more than 9% as recently as 2008. Now it’s crawling along at barely above 2%.
• India’s current annualized growth rate of 4.5% is less than half of what it was as recently as early 2010.
• China, the driver of global demand, needed to slow its own growth to stave off inflation and asset bubbles — but it might have overshot to the downside. The economy, which was expanding by nearly 12% a year as recently as 2010, is now struggling to break above 8%.

If you’re looking for moonshot growth potential — and have a huge appetite for risk — then you need to start poking around of the globe. One increasingly attractive area might be found in the frontier markets sub-Saharan Africa.

South Africa is hardly a secret as a promising emerging market. It was even added to the BRIC club a few years back. (The BRICs are now called the BRICS to reflect the country’s inclusion.) However, with annualized growth of just 2.5%, South Africa’s economic performance isn’t much to get excited about.

But outsized opportunities might abound elsewhere among the continent’s more than 40 nations — notably in oil-rich Nigeria, the region’s most populous country.

General Motors (NYSE:GM) said Thursday that Africa’s burgeoning middle class will boost annual car sales by 20% in the next two years. That increase will be driven predominantly by South Africa and northern Africa for now, but after that, Nigeria stands as the next big growth market.

Indeed, Africa is in the midst of an inexorable and virtuous demographic boom that should propel economic growth for a generation or more.

More than 70% of Africa’s total population is under age 35 — and 40% is younger than 17 — according to research from Accenture, making it the youngest continent in the world.

The demographic boom represents some serious future consumer firepower. As that cohort enters the work force and hits its prime spending years (joining a middle class already numbering roughly 300 million people), consumer expenditures in sub-Saharan Africa are forecast to soar, rising 65% to nearly $1 trillion by the end of this decade.

At the same time, sub-Saharan Africa is also abundantly rich in commodities such as oil, natural gas, copper, iron ore and gold.

No wonder the International Monetary Fund projects sub-Saharan Africa to replace Asia as the world’s fastest growing region over the next decade.

However, retail investors wishing to gain exposure don’t have a lot of options.

There are few ADRs listed on U.S. exchanges, and the ones that do exist are for companies in South Africa. Although a handful of companies based in Nigeria and Malawi trade on the London Stock Exchange through ADRs, that doesn’t much help U.S. investors.

As for mutual funds and exchange-traded funds, they mostly afford exposure to South Africa, north African countries such as Egypt and Morocco, and the oil-rich Gulf States. (The mutual fund options also tend to have the disadvantage of sporting loads and/or relatively high expenses.)

To get some broader geographic exposure to sub-Saharan Africa — and relatively low fees — you pretty much have to go with Market Vectors Africa Index ETF (NYSE:AFK). True, AFK isn’t a pure play, and its geographic reach is still fairly circumscribed, heavily weighted toward Nigeria (as well as South Africa, with Egypt and Morocco also in the mix). And AFK also includes lots derivative plays on sub-Saharan Africa through holdings in U.K., Canadian and Norwegian companies doing business there.

That said, four of the top six holdings are Nigerian investments, and Nigeria comprises 25% of the portfolio. AFK also counts a position in a Kenyan financial company in its top 25 holdings. And — importantly — the net expense ratio is an investor-friendly 0.78%.

The market’s sure to see the launch of new investment products if investor demand for exposure to sub-Saharan Africa picks up. For now, it’s probably just as well that there aren’t more options.

As we’ve written before, when it comes to investing in frontier markets, retail investors should allocate no more than the thinnest sliver of a portfolio to these risky, speculative bets.

As of this writing, Dan Burrows did not hold a position in any of the aforementioned securities.