The U.S. Border Patrol (Border Patrol), an office within the Department of Homeland Security's (DHS) U.S. Customs and Border Protection, uses an annual recidivism rate to measure performance of the Consequence Delivery System (CDS)-a process that identifies consequences as Most Effective and Efficient to deter illegal cross border activity in each sector-however, methodological weaknesses limit the rate's usefulness for assessing CDS effectiveness. GAO found that Border Patrol's methodology does not account for an alien's apprehension history beyond one fiscal year and neither accounts for nor excludes apprehended aliens for whom there is no record of removal after apprehension and who may have remained in the United States without an opportunity to recidivate. GAO's analysis of recidivism for fiscal year 2015 considering these factors showed a 29 percent recidivism rate, compared to Border Patrol's 14 percent recidivism rate. Border Patrol could more accurately assess recidivism and CDS effectiveness by strengthening its recidivism rate methodology, such as by using an alien's apprehension history beyond one fiscal year and excluding aliens for whom there is no record of removal from the United States.