“High turnout has been maintained by a combination of three factors: a strong culture of civic participation, supportive election laws and competitive elections,” said Burden. “The participatory culture probably did not change substantially since the last election. The more likely culprits are changes in election laws and the competitiveness of the 2016 campaign.”

The study focused on other factors that could be driving increased voter turnout, such as same-day voter registration, all voters receiving a mail-in ballot, nonpartisan redistricting and ranked-choice voting. Pillsbury said it didn’t look at voter ID because there are conflicting studies on its impact on voting, something that could clear up over time, and also because Nonprofit VOTE tries to stick to less-partisan issues.

Wisconsin’s 2011 voter ID law was put on hold until last year due to legal challenges. The U.S. Supreme Court declined to hear a challenge to the law, leaving an appellate court’s ruling upholding the law in place. Republicans supported the law as a safeguard against voter fraud, while Democrats said it discouraged minorities, students and seniors from voting.

Lowest since 2000 election