National: The mathematician who’s using geometry to fight gerrymandering | PRI
After every new US census, states have to redraw their congressional districts to divide up their populations fairly. But in practice, these districts don’t always end up equal: Federal judges recently ordered Wisconsin lawmakers to redraw maps of the state’s legislative districts, after finding the districts had been shaped to favor Republican candidates. Allegations of gerrymandering are also playing out in states like Texas and North Carolina. So what does a gerrymandered district even look like on a map? More like a carved-out jigsaw piece than a rounded blot, as it turns out. But as Tufts University mathematician Moon Duchin explains, gerrymandering can be difficult to prove, even when something about a district’s shape seems fishy. “We’ve had justices saying that, ‘We know a bizarre, irrational shape when we see it, but we don’t know what precisely should the threshold be which makes a shape too tortured, or irregular, or unreasonable,’” she says. (Take a closer look at district shapes across the US.)