Quasi-Experimental Evaluations of Border-Enforcement Measures

In this article, we seek to establish a causal connection between border-enforcement actions or policies and metrics that might be used to measure relevant outcomes at the border. Applying quasi-experimental methods, we investigate the impact of surveillance technology on levels of U.S. Border Patrol apprehensions of unlawful border-crossers between ports of entry along the southwest border. Our analysis offers insights into some of the effects of surveillance technology and serves as a demonstration of concept for the usefulness of such statistical methods. The most robust finding is that deploying one type of technology – integrated fixed towers (IFTs) – is associated with decreased apprehension levels in the zones of deployment. Although we emphasize ambiguity in the meaning of the results and the uncertainty in statistical inference with relatively small numbers of deployments, we conclude that there is strong evidence that some migrants were deterred from crossing surveilled areas of the border. The results are more inconclusive for other surveillance assets, but there are suggestions that some may elevate apprehension levels, pointing to a boost to the U.S. Border Patrol’s situational awareness. Statistical methods both hold promise and have limitations for the study of the impact of border-enforcement measures beyond the analysis in this study. Although these methods cannot, on their own, yield clear answers in every case, they do have the potential to help policymakers understand and anticipate the impact and effectiveness of different border-enforcement measures.