Thousands of Wisconsin residents in two counties did not cast ballots in last November’s presidential election due to confusion over the state’s voter ID law, according to new research.

The study, which was conducted by a political science professor at the University of Wisconsin-Madison, determined that 11.2 percent of “eligible nonvoting residents” were discouraged by the state’s voter ID requirement. This percentage amounts to 16,801 individuals in Wisconsin’s Milwaukee and Dane counties, although as many as 23,252 individuals may have been dissuaded, given the survey’s margin of error.

“The main conclusion of the study is that thousands, and perhaps tens of thousands, of otherwise eligible people were deterred from voting by the ID law,” Kenneth R. Mayer, the professor, said in a statement.

{mosads}Mayer noted that the 11.2 percentage does not incorporate Wisconsin voters who do not have identification and therefore fail to register.

“And while the total number affected in Milwaukee and Dane Counties is smaller than the margin of victory in the 2016 presidential election, that is the wrong measure,” Mayer said. “An eligible voter who cannot vote because of the ID law is disenfranchised, and that in itself is a serious harm to the integrity to the electoral process.”

Wisconsin last November voted for the Republican nominee for the first time since 1984, with President Trump defeating Democrat Hillary Clinton by fewer than 23,000 votes.

The University of Wisconsin study also concluded that the state’s voter ID law dissuaded more minority and low-income voters from voting than those in higher-income brackets. The law discouraged 8.3 percent of white registered voters, researchers found, compared to 27.5 percent of African-American voters. And 21.1 percent of individuals with a household income below $25,000 were discouraged from casting ballots, compared 7.2 percent of individuals making more than $25,000.

Wisconsin voters for the first time in 2016 were required to show identification in order to vote in a general presidential election.