The use of robots in U.S. workplaces has more than doubled since the Great Recession, but the impact has hit certain areas of the country — and segments of workers — more than others.

A recent report from The Century Foundation found Midwestern states such as Michigan, Ohio, Indiana, Illinois and Wisconsin saw the sharpest growth in robots being used in the workplace from 2009 to 2017, and these areas now have the highest levels of “robot intensity” in the country.

Robot intensity refers to the number of industrial robots per 1,000 human workers. The higher the number, the more robots there are in the workplace alongside humans.

Areas with the highest robot intensity are home to some of the of the biggest manufacturing industries in the country. Factory and production jobs have been proven to be highly susceptible to automation when robots and other automated machinery are able to do physical, routine work very quickly at high volume.

Nationwide, there are about 0.34 robots per every 1,000 human workers. But that number varies widely depending on the city.

Jennifer Liu, CNBC