"CBP has not developed metrics that systematically use data it collects to assess the contributions of border fencing to its mission," the report said on Thursday.
The border security agency spent about $2.3 billion to deploy fencing from 2007 through 2015 and constructed 654 miles of fencing, the report said.
The document read that the agency has also failed to use available data to "determine the contribution of surveillance technologies to border security efforts" and is unable to gauge the effectiveness of other tactical infrastructure such as roads, lighting, and cameras.
CBP has responded to GAO concerns with plans to develop metrics by January 2019, according to the release.
President Donald Trump is pushing to replace much of the border’s existing fence with a see-through wall.