States that have enacted voter identification laws requiring citizens to use a photo ID to prove their identity had 4.4 percentage points lower voter turnout compared to states that did not, according to a new report from political scientist Michael P. McDonald. The release of the figures comes just days after this year’s midterm elections and after a number of traditionally conservative states have introduced voter ID laws that critics have asserted are meant only to disenfranchise Democratic voters.

McDonald’s report, first highlighted by, also found that states that enforce a non-photo ID law also reported a turnout 1.52 points lower than states that don’t have voter ID laws of any kind. These numbers are just the latest to suggest that voter ID laws, generally passed by Republican lawmakers in states where competitive races are normal but voter fraud is not, have been used to turn away eligible voters who simply don’t meet often obscure identification requirements. Competitive races tend to increase turnout, though separate research from the Brennan Center for Justice shows that turnout is actually lower when competitive races are conducted in states with ID laws.

About 37 percent of all Americans voted in the 2014 midterms, the lowest number in the last five elections. In 2006, 40.4 percent of Americans voted and 40.9 percent voted in 2010. To boost this figure political scientists have suggested enacting same-day voter registration, early voting, mail-in voting, ending felon disenfranchisement and other measures that are almost universally opposed by Republicans in states where the laws would make the most difference.

Vermont Sen. Bernie Sanders, an Independent, said Friday he’ll try to rectify low turnout by sponsoring a bill that would make Election Day a federal holiday, thereby giving most Americans the day off from work.

“In America, we should be celebrating our democracy and doing everything possible to make it easier for people to participate in the political process,” Sanders said in a news release. “Election Day should be a national holiday so that everyone has the time and opportunity to vote. While this would not be a cure-all it would indicate a national commitment to create a more vibrant democracy.”