Border Security Metrics: Progress Made, but DHS Should Take Additional Steps to Improve Information Quality

What GAO Found

In its fiscal year 2019 Border Security Metrics Report , the Department of Homeland Security (DHS) reported information on 37 of the 43 metrics required by the National Defense Authorization Act for Fiscal Year 2017 (NDAA). As shown below, GAO found that 18 of the 37 metrics in the fiscal year 2019 report generally corresponded with their descriptions in the NDAA, while 19 metrics differed, such as in scope or calculation.

How the Department of Homeland Security (DHS) Reported on the 43 Metrics Required by the National Defense Authorization Act for Fiscal Year 2017 (NDAA)

DHS improved the quality of information in several metrics in the fiscal year 2019 report compared with earlier versions. However, data reliability issues remain—such as DHS not fully disclosing limitations of some metrics—because DHS does not have a process to systematically review the data. Implementing GAO's prior recommendations to develop and implement a process to systematically review the reliability of data—and communicate limitations identified through this process—would position DHS to maximize the quality of information and provide Congress and the public with contextual information needed to evaluate the metrics.

DHS used a statistical model to estimate four metrics, including the estimated number of undetected unlawful entries between ports of entry. In response to one of GAO's prior recommendations, DHS, in its fiscal year 2019 Border Security Metrics Report , showed how the sensitivity of three assumptions affected the precision of the model's estimates. For example, the model assumed that DHS apprehends all families unlawfully crossing the border, and the fiscal year 2019 report outlined how this assumption affected the model-based metrics in 2018. This sensitivity analysis will allow Congress and the public to better understand the limitations of DHS's model and better evaluate the validity of border security metrics derived from it.

In response to another GAO recommendation, DHS conveyed statistical uncertainty for one of the unlawful entry metrics in its fiscal year 2019 report. In particular, DHS outlined how this uncertainty might affect the model-based apprehension rate. However, DHS did not report how uncertainty would affect the other three metrics that rely on its statistical model. As GAO previously recommended, including measures of statistical uncertainty for all relevant metrics in future reports would allow Congress, policy makers, and the public to more fully evaluate the extent to which the metrics are valid.

Why GAO Did This Study

The United States has approximately 6,000 miles of land borders, 95,000 miles of coastline, and more than 300 ports of entry where travelers and cargo are inspected. Securing U.S. border areas is a key part of DHS's mission, and its ability to measure border security activities is essential to managing its responsibilities effectively and efficiently.

The 2017 NDAA requires DHS to report annually on 43 border security metrics. The act also includes a provision for GAO, within 270 days of receipt of the first report and biennially for the following 10 years, to review and report on the data and methodology in DHS's report.

GAO issued its initial report in March 2019. This second report evaluates the report DHS issued in August 2020, which is known as the fiscal year 2019 report and contains data through fiscal year 2018. This report addresses the extent to which DHS (1) reported metrics outlined in the 2017 NDAA using quality information and (2) has taken steps to determine and convey the sensitivity of key assumptions and the statistical uncertainty of its unlawful entry metrics. GAO assessed the methodology and data in DHS's report, analyzed DHS's use of statistical modeling, and interviewed officials from DHS offices and components.