I want to tell you about my favorite equation in the world. It goes like this:

E = P × V

That’s read as “the expected value of an event is the value of the event times the probability the event happens.”

It’s amazing how often that comes up – especially in discussions about insurance, computer security, and the famous wall.

During the recent kerf lawful (I meant “kerfuffle” but I like that better) over Trump’s desire for a border wall or barrier or whatever the hell they are calling it now, Dan Crenshaw — whom I may like almost as much as I like that equation — tweeted about the wall.

Ah yes, the tunnel myth. Because it’s so easy to build tunnels. No one would ever notice. Might as well just do nothing, now that the tunneling option has been exposed. Can we have a serious conversation now? That’d be great. https://t.co/16RDlBQoVm — Dan Crenshaw (@DanCrenshawTX) January 10, 2019

This was immediately followed by a succession of tweets to the effect of, “Ha ha ha tunnels! Ackshully, walls don’t work.”

Which brings us back to the equation. Now, let us assume for the sake of argument that each illegal immigrant comes with an associated cost. That means the expected cost of illegal immigration is basically proportional to how hard it is to get into the country as an illegal immigrant.

Here’s the fact that clearly has been kept secret from these city folk, who I’m sure have never dug so much as a post hole: digging tunnels is hard. Digging tunnels secretly is really hard. (Go watch “The Great Escape” or read about the Tunnel 57.)

Drug dealers can dig tunnels because drug dealers make lots and lots of money and so can afford to pay peónes to dig their tunnels. But then, drug dealers have enough money that they’re building submarines to smuggle drugs.

You may have doubts about whether walls or barriers or beautiful steel whatever-the-hell are the best solutions. God knows I do. (Among other things, the eminent domain suits will long outlast the Trump presidency.) But no one with even a half a lick of sense or any experience tilling a garden plot doubts that digging a tunnel is lots harder than walking across the border. And if it’s harder, the likelihood of that happening is smaller. So yes, a wall will deter illegal immigration — as well as all of the other things that cross the border — even though it is possible to dig a tunnel.