A report by Congress' watchdog says the United States still does not have a way to measure how well fencing works to deter illegal crossings from Mexico.
President Donald Trump is moving ahead with plans to erect a wall along the border. But the Government Accountability Office says in a report issued Thursday that ways to evaluate the effectiveness of border barriers should be developed first. Congressional leaders say the wall could cost up to $15 billion.
Fencing currently covers about 650 miles of the 2,000-mile border, much of it built during President George W. Bush's second term. The report says fence construction cost $2.3 billion from 2007 to 2015.
The report estimates that fencing costs an average of $6.5 million a mile to build.