Investors are pulling out of emerging markets, and plunging commodities prices are hitting growth in much of the developing world. But largely unnoticed by many U.S. investors, a group of medium-to-large cities in those markets is emerging as possible future powerhouses.

They are places like Luanda, a fast-growing Angolan metropolis of 10 million that many Americans have never heard of, or Suzhou, a city of 5 million near Shanghai whose population is growing at a rate of 6.5 percent a year, according to a recent United Nations report. And those midtier cities are seeing consumer spending that’s sometimes growing even faster than their populations.

“The cities that are growing are an unexpected bunch. These are the unknown cities,” said Saskia Sassen, a sociologist at Columbia University.

Megacities like Tokyo and Sao Paolo grab headlines, but the fastest population growth is happening in a group of global second-tier cities, which are easier for rural populations to reach and are safer and less intimidating than the megacities, many of which are surrounded by vast slums, Sassen said.

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