Do we really need a wall on the Mexican border? It would improve security at that border, but there is another, apparently larger source of uncontrolled illegal immigration: Nonimmigrant alien visitors who are admitted for temporary periods of time and stay longer than permitted.

A report issued by three Yale-affiliated researchers in September 2018, estimates that there are 22.1 million undocumented aliens in the United States, and that approximately 9 million of them (41 percent) entered as nonimmigrant visitors and overstayed their admission periods.
A wall
Many countries have border walls. There were only seven border walls or fences in the world at the end of World War II, but there are at least 77 of them now.
David Frye explains in his book, Walls: A History of Civilization in Blood and Brick, that barriers to keep others out are as ancient as human civilization.
The main argument against putting one on the Mexican border is that a dramatic drop in the apprehension of illegal crossers proves that we already have good border security there.
From the 1980s to the mid-2000s, the government annually apprehended between 1 and 1.6 million illegal crossers at that border. But annual apprehensions have been below a million since fiscal 2007, and they were down to 303,916 in fiscal 2017.
Are apprehensions a reliable way to estimate how many illegal crossings are occurring? Would you accept a decline in the apprehension of drug smugglers as proof that fewer drugs are being smuggled across the border, or would you wonder whether the drug smugglers had found better ways to cross without being detected?
Realistically, we have no way of knowing how often drugs or undocumented aliens are smuggled across the border without being detected.
Published originally on The Hill.
Nolan Rappaport was detailed to the House Judiciary Committee as an executive branch immigration law expert for three years. He subsequently served as an immigration counsel for the Subcommittee on Immigration, Border Security and Claims for four years. Prior to working on the Judiciary Committee, he wrote decisions for the Board of Immigration Appeals for 20 years.

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