Even before there was President Trump, there was “the wall.” America has spent billions on border enforcement, which includes a barrier between the US and Mexico. And the current administration’s nationalistic promises to put “America first” have given the border wall heightened symbolic importance. But it’s not clear just how effective it is in actually preventing migrants from entering the US. Ben Feigenberg says the wall does, in fact, have a substantial impact on the number of people crossing the border. In the July issue of the American Economic Journal: Applied Economics, he says that construction of a border fence reduced migration by up to 35 percent. However, that doesn’t seem to be any more cost-effective than hiring more border patrol agents. The AEA’s Chris Fleisher spoke with Feigenberg about what his research says about the effectiveness of border walls, potential unintended consequences, and how economics can inform debates around policing and criminal justice. *Theme music is by Sound of Picture.