The more Wal-Mart stores a county has, the more likely it is to have active hate groups in the area, according to Penn State economists.

"Wal-Mart has clearly done good things in these communities, especially in terms of lowering prices," Stephan Goetz, professor of agricultural economics and regional economics, explained. "But there may be indirect costs that are not as obvious as other effects."

The study, published in Social Science Quarterly, found that the number of Wal-Mart stores was a better predictor of hate group participation than the unemployment rate, high crime rates and low education.

There were 1,018 active hate groups in the United States in 2011, according to the Southern Poverty Law Center, up from 1,002 in 2010.

The researchers believe that the correlation between Wal-Mart and hate groups exists because of breakdown of the community. Small local businesses are more likely to be members of civic groups and involved in the community. They are also more likely to have closer relationships among their employees.

"While we like to think of American society as being largely classless, merchants and bankers are part of what we could call a leadership class in a community," Goetz said.

In contrast, people are more likely to feel alienated by big-box retailers like Wal-Mart, the researchers explained. They noted that areas that had Wal-Mart stores were also likely to have other big-box retailers, like Target.

"We're not trying to pick on Wal-Mart," said Goetz. "In this study, Wal-Mart is really serving as a proxy for any type of large retailer."

"We doubt strongly that Wal-Mart intends to create such effects or that it specifically seeks to locate in places where hate groups form," the researchers said.

Anil Rupasingha of New Mexico State University and Scott Loveridge of Michigan State University co-authored the study.