In a piece published in the Journal of Conflict Resolution, we find that border fortification construction is a growing global phenomenon and argue that cross-border economic inequality is the critical factor leading states to construct border walls. The mechanism in our argument is that cross-border inequality drives illegal immigration from the poorer state into the wealthier state. In response, the wealthier state constructs border fortifications, such as a wall. We find little systematic evidence that security considerations, such as guarding against a territorial rival, play a primary role in motivating the construction of border fortifications. In other words, the processes motivating the construction of a border wall between the United States and Mexico extend globally, and some prominent examples of security driven fortification construction, such as the French Maginot Line (constructed largely out of fear of attack from neighboring Germany), are exceptions to the more general reason that states build walls. We test this argument by introducing new data on the construction of border walls from 1800 to 2013. The broader policy implications of this work was discussed here.
In a piece published in International Organization, we find that border fortification leads to a reduction in trade between countries. The mechanism in our argument is that border fortifications heighten the well known "Border Effect": the idea that borders, by their very nature, slow and inhibit trade. We test this claim using the latest modifications in the gravity model of trade. When combined with our first paper, the two papers show how the post-Cold War surge in border wall construction is a "concrete" form of state backlash to economic globalization.
Beyond the intellectual contributions, this project is exciting for three reasons. First, it is a clear combination of our respective research interests (mine on the political-economic determinants of arms acquisition and creation; David’s on the determinants of international borders and the drivers of territorial disputes). Second, this is a highly active area of new research, as we are not the only research team collecting and analyzing data on border walls. As Ron Hassner (a member of one of the other teams) and I discussed at panel during the 2016 International Studies Association annual meeting, our teams worked independently and yet came across similar findings regarding the construction of walls. Third, this is a very timely topic. Our research has been used by media outlets (such as The New York Times) and led us to be invited to a May 2018 workshop by Beth Simmons at the Perry World House titled “International Barriers in the Globalized World”.