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As the ideological gaps between Democrats and Republicans appear to grow increasingly wider, there is now new data that shows what could be driving that political divide.

“We tend to think humans behave unpredictably, but more and more we see that, in a lot of settings, human choices can be explained by abstract and elegant models,” said Boleslaw Szymanski, a computer science professor at Rensselaer Polytechnic Institute.

By analyzing millions of roll call votes in U.S. Congress over the past 60 years—through the rise of the Civil Rights movement and the Vietnam War—Szymanski and his colleagues created a parameter to determine what drives the polarization of members of the legislative body, what the authors call “polarization utility.”

This driving force measures how much benefit members of Congress can get by focusing on the issues that appeal to their supporters, the researchers said.

The two factors that drive polarization utility: polarized voters and the increasing influence of campaign donors, which is driven by the growing cost of campaigning, according to the study, published Tuesday in the Journal of the Royal Society Interface.

“This means that, if we want to encourage or discourage polarization of the Congress, we can do so by changing the utility,” said co-author Jianxi Gao, an assistant professor of computer science at Rensselaer.

The authors suggest that two ways to change the polarization utility might be changing campaign donation limits and the length of terms legislators serve, but they are not calling for any action to be taken.

“Whether we want polarization and how much is not a decision for us scientists,” Szymanski said, “but rather for society as a whole.”