Indiana’s sharp rise in union members is due to its robust economic growth and increase in manufacturing jobs, while Illinois’ economy continues to lose factories and sees little growth in union members.

The average cost of workers’ comp for steel workers among neighboring states is under $8 per $100 of payroll compared to nearly $12 in Illinois.

Insurance premiums cost 20 percent of payroll for concrete construction workers in Illinois.

The industry giant’s move comes amid continued disinvestment in Illinois manufacturing.

In February 2012, Caterpillar’s then-CEO Doug Oberhelman outlined needed reforms to save Illinois manufacturing jobs. State lawmakers have failed to act, and the Land of Lincoln is the only state in the region to lose manufacturing jobs since.

There are 170,000 fewer people working in Illinois since before the Great Recession.

In the last decade, Illinois’ economy and the economies of neighboring states have gone in opposite directions, with more people now working in Wisconsin and Indiana combined.

The company’s announcement affects 800 hourly employees, though 1,200 workers will remain in Aurora. In January, Caterpillar announced plans to relocate its global headquarters to Chicago and out of its longtime hub in Peoria.