Streamline is an initiative to criminally prosecute individuals who illegally enter the United States through defined geographic regions along the Southwest border. Although U.S. Customs and Border Protection’s (CBP) Border Patrol measures Streamline’s effect on re-entry of illegal aliens, its metrics do not reflect an alien’s crossing history, re-entry, or re-apprehension over multiple years. As a result, Border Patrol is not fully and accurately measuring Streamline’s effect on deterring aliens from entering and re­entering the country illegally. Additionally, because Border Patrol does not distinguish Streamline costs from the costs of its other border enforcement consequences, Border Patrol is not able to differentiate Streamline-associated costs. Finally, according to ICE ERO, Streamline has increased the workload at some of its Southwest border field offices. However, ERO cannot be certain which aliens it removes as a result of Streamline and which removals result from other enforcement actions.