Every state requires voters to produce some evidence they are eligible to vote, but Indiana’s photo identification requirements are the most stringent.The Supreme Court will soon decide whether the state can require official photo ID to cast a regular ballot at the polls.If the law is upheld, several other states are likely to follow Indiana’s example.

Opinion polls suggest most people find voter ID laws to be reasonable precautions against ballot stuffing; however, many progressive activists consider these reforms undemocratic and discriminatory. They argue such laws are unnecessary because voter impersonation at the polls is a myth, and they worry identification requirements unduly burden eligible voters, especially minorities, the elderly, poor and less educated.

Armed with this intuition, opponents of the photo ID law have made dire predictions about declining voter turnout, particularly among disadvantaged groups.Such claims are easily tested, but the public debate has nevertheless been mostly unencumbered by facts.

First, decades of social science research indicate voter identification requirements should have at most negligible effects on turnout.This is because there are already many hurdles to casting a ballot, from taking an interest in public affairs to registering to vote and bothering to remember where and when to vote.Almost all nonvoting is explained by these mundane factors.

For example, the 2006 Current Population Survey from the U.S. Census Bureau contains information on the voting behavior of about 85,000 people; among eligible voters who did not vote, 94 percent were either not registered to vote, forgot to vote or weren’t interested in voting, etc​.So the few folks who don’t have official photo identification are already unlikely to be voters for any number of reasons unrelated to voter identification requirements at the polls.

But those eligible voters with the wherewithal to register, study the candidates, remember where and when to vote and get themselves to the polls are unlikely to be deterred by the added requirement of photo identification. Fewer still are incapable of producing identification if so motivated.

Second, while most of the remaining nonvoters give undescribed “other” reasons for not voting, just less than 2 percent of eligible nonvoters do cite registration problems as their primary reason for not voting.This figure includes people who are not properly registered and perhaps some who merely lack proof.These nonvoters, however, are not disproportionately located in Indiana, despite that state’s more restrictive ID requirements.Nor is it the case that minority, less educated, elderly or poor Indiana citizens are more likely to be nonvoters because of registration problems.Therefore, self-reported voting behavior should allay most concerns about photo ID.

Third, actual election returns further demonstrate Indiana’s law did not have a negative impact on voter turnout.The 2002 and 2006 midterm elections straddle the implementation of the photo ID requirements in Indiana and so offer a natural experiment to test effects on turnout.I have examined county-level election returns from Indiana before and after photo ID, and voter turnout actually increased about 2 percent.Nor was turnout relatively lower in counties with greater percentages of minority, less educated, elderly or poor voters.These findings are robust to a variety of statistical assumptions and hold up when more years are included in the analysis.

The final reason voter turnout is unlikely to change much in the wake of photo ID is that voter impersonation is itself probably rare.Despite popular concerns that too many ineligible votes are cast in elections, many progressives ridicule the idea of voter fraud at the polls.The choice of words is key; “fraud” requires intent and is understandably difficult to prove.But do voter identification laws prevent ineligible votes from canceling out legal votes?

An indication comes from the 2000 Current Population Survey.Respondents were asked whether they had moved in the past five years and whether they had registered to vote in the past five years. More than 10 percent of respondents — both nationally and in Indiana — self-reported they were not registered at their current residence but voted anyway.Of course, some of these responses might be in error, but the implication is a non-trivial number of improper ballots are cast in a typical elec​tion​.So even absent irrefutable proof of vote fraud, there is still good reason to check voter ID at the polls.

Photo ID prevents ineligible voters from entering the voting booth and induces otherwise eligible voters to update their registration ahead of time.Reasonable people might weigh the benefits and costs differently, but one thing is certain:Far from being a nefarious contrivance to disenfranchise vulnerable citizens, Indiana’s photo ID law is nothing more than a common-sense means to administer elections more effectively and fairly for all citizens.