Liberal observers are astonished and thrilled that Judge Richard Posner, the most influential judge sitting on the federal bench, has written a scathing condemnation of Wisconsin voter ID laws. Posner was appointed by Ronald Reagan, and his law-and-economics approach with its libertarian overtones can in a certain sense be described as conservative. Notably, Posner wrote a 2007 opinion upholding Indiana’s strict voter ID law — an opinion subsequently upheld by the Supreme Court. Now, it would seem from the headlines, Posner has reversed himself. Newsworthy, right? Well, sort of. A close reading of Posner’s opinion indicates that the judge hasn’t so much reversed his earlier view as he has taken seriously data that were unavailable in 2007. The numbers, as Posner now interprets them, do strongly suggest that the purpose of voter ID laws is to make it more difficult for poor people, especially blacks and Latinos, to cast votes. According to Posner, he wasn’t wrong in 2007. It’s just that then, there was no basis to assume that Indiana was trying to exclude minority voters. Now, there’s evidence in favor of that view. A careful look at Posner’s opinion is an object lesson in how a rational person should reconsider initial presumptions in light of new evidence — an approach pioneered by the British statistician Thomas Bayes in the 18th century and now dubbed Bayesianism. When Posner had to analyze the Indiana statute, he made much of the fact that, as he now puts it, “there was no evidence that the Indiana law was likely to disenfranchise more than a handful of voters.”
One of Posner’s then-colleagues, Bill Clinton-appointee Terence T. Evans, depicted the Indiana voter ID law as “a not too thinly veiled attempt to discourage election day turnout by certain folks believed to skew Democratic.” But, as Posner pointed out in his most recent opinion, Evans “cited no evidence to support his conjecture.” In Posner’s current view, Evans was “prescient” — but prescience is a form of prophecy, not a form of reasoning based on evidence. Posner believes that he was correct not to take account of his colleague’s speculations in 2007.
Since then, the nature of the evidence has changed. According to Posner, in the 2007 case, 1 percent of Indiana’s population lacked the relevant ID. Yet 9 percent of registered voters in Wisconsin lacked the documents required by its state law. Posner went on to describe the extraordinary “litany of practical obstacles” a person would have to overcome in order to vote without a driver’s license in Wisconsin. He added that although Indiana’s voter rolls were inflated by as many as 1.3 million people, “there is compelling evidence that voter-impersonation fraud is essentially nonexistent in Wisconsin.” Posner was apparently impressed by an expert witness who had “studied Wisconsin elections that took place in 2004, 2008, 2010, and 2012 [and] found zero instances of in-person voter-impersonation fraud.”