From the Document: "Understanding the risks present at the U.S. borders and developing methods to measure border security are key challenges for the Department of Homeland Security (DHS) and the U.S. Border Patrol, the agency within DHS charged with securing the border between ports of entry. Metrics for border security are used at both the strategic level, by DHS, and at the operational level by Customs and Border Protection (Border Patrol). This report reviews DHS's and the Border Patrol's use of metrics in evaluating their objective to secure the border between ports of entry. DHS and the Border Patrol can use metrics to measure their performance and estimate risks at the border. Additionally, metrics provide Congress with an understanding of DHS's and Border Patrol's progress in securing the border. At a strategic level, DHS uses performance metrics to understand its ability to meet border security objectives. However, DHS has struggled to create a comprehensive measure of border security. Most recently, DHS has labored to create a new generation of performance metrics, through the estimation of unauthorized entry of migrants into the United States. This measure represents the volume of migration entering the United States and can be influenced by factors outside of DHS's control, and therefore may not directly speak on border security. Congress may want to consider whether this is an adequate performance metric for border security and whether additional and/or more comprehensive and targeted metrics are required."
CRS Report for Congress, R44386
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html