After announcing the closure of his short-lived commission to end voter fraud, President Trump made it clear Thursday that he wants more states to require identification at the ballot box to prevent what he believes is rampant—but still unproven—election rigging. Ever since the Supreme Court struck down a key part of the Voting Rights Act in 2013, laws requiring voters to show identification when they vote have speckled the nation, popping up in states from Rhode Island to Arizona. Almost as quickly, voting rights advocates have taken states like Texas and Alabama to court, arguing that these laws intentionally discriminate against minority voters. Just last summer, a federal judge tossed out Texas’s voter ID law, in a case that’s now being revisited by an appeals court. But proving exactly how discriminatory these laws are requires far more complexity than it might seem.
Sure, there are endless anecdotes of well-meaning, well-prepared citizens being turned away on election day, but anecdotes are not data. There are ample surveys asking voters whether these laws came between them and the ballot box, but people can always misrepresent themselves on surveys, and courts tend to dismiss them, anyway. Seven states include Social Security numbers in voter files and driver’s license records, but across the rest of the country, determining whether a single individual voter is also listed in any number of identification databases has become a complex and nettlesome problem for voting access advocates and statistics researchers alike.
Recently, however, researchers at Tufts University and Harvard University demonstrated that it’s possible to match individuals across government databases with nearly perfect accuracy, using just a few basic identifiers like a person’s name, date of birth, and address. They developed the algorithm while working as expert witnesses in the Department of Justice’s case against Texas. Now, in a newly published paper, researchers Stephen Ansolabehere of Harvard and Eitan Hersh of Tufts have explained the underlying methodology. Their goal, according to Hersh, is to create a system courts can easily understand, which can not only be used in future voter ID law cases, but can also help dispel some myths about who those laws do and don’t hurt.
“The more we can agree on methods that are easy to explain, the better off we are,” says Hersh.