As someone who spends a good portion of the year living a short distance from the southern border in Arizona and doing humanitarian aid work here, I promise you that walls and fences do not stop undocumented immigration. They do not even slow it down by very much.

What walls and fences do is force people into the hands of the cartels and help maintain the border industrial complex.

It's also really important to keep two things in mind when you read these numbers coming out of the Border Patrol: one is that many of these "apprehensions" are repeats. In other words, the same person was caught several times and therefore counted several times. The second is that many if not most of these people are asylum-seekers, crossing the border and turning themselves in. This is legal, other than not crossing at a port of entry.