Unlike prison perimeters, borders can be thousands of miles long, which makes them difficult to monitor properly. The US employs more than 20,000 Border Patrol agents; but even if they were all on duty at the same time, each would need to guard a 1,700-foot section of the border.
和监狱不同，边境可能长达数千英里，这意味着很难对其进行恰当的监控。美国边防局雇用了20,000名雇员；但即使他们同时出勤，每人也需要看守1,700英尺长的边境线。