Sears is closing hundreds of stores around the country Wikimedia Commons Poverty has been creeping into the suburbs for the last 20 years, and the rise of online retailers could be making it worse.

According to a new book, "Places in Need: The Changing Geography of Poverty," by University of Washington professor Scott Allard, American suburbs are facing economic hardship on a massive, if poorly understood, scale.

As of 2014, urban areas in the US had 13 million people living in poverty. Meanwhile, the suburbs had just shy of 17 million.

The Great Recession of 2008 helped accelerate much of the poverty that emerged in the early 2000s, Allard's research has found. But another disrupting factor was the technological shift that enabled — and continues to enable — online retailers like Amazon and other e-commerce sites to replace shopping malls and big-box stores.

This ongoing demise has hollowed out many of the jobs suburban Americans once turned to as a means of supporting themselves.

"When we think about the current labor market, there's reason to be concerned about the disappearance of good-paying, low-skill jobs," Allard told Business Insider.

His research has found that even when the US began its climb to economic recovery in the 2010s, the suburbs continued to sink into poverty. More jobs sprang up, but not the kinds that helped people live secure lives. Most are part-time positions with low wages.

The kinds of jobs that do entice younger people — mostly higher-skill, white-collar work — are increasingly found in cities. Suburban office parks are becoming a thing of the past as millennials flock to nearby metropolitan areas for work, accelerating the speed at which the suburban workforce hollows out overall.

Allard said it's a reversal of several decades ago, when businesses moved to the suburbs to attract people who had recently vacated the city in search of a safer, greener place to live.

Manufacturing — which largely took place in cities in the 1960s and '70s — left for the suburbs a few decades after. Today, Allard sees the manufacturing industry making yet another migration.

"I think those economic realities have happened in suburbs over the last twenty-five years with automation and jobs moving to other parts of the globe," he said. As a result, low-skill and low-education workers "are struggling to find good-paying jobs."