While none of these was billed as “closure” when it occurred, Josiah Heyman argued that even a marked slowdown equals a closure for truck drivers and for people who commute through the border.

He said it’s hard to imagine what kind of ripple effect a full-on closure would have.

“I’d like to speak up for the border when I say there are millions of people here, and we have jobs and families and lives that interact with it every day,” said Josiah Heyman, a professor who studies the border at the University of Texas at El Paso and pointed out that a lot of US citizens live and work on both sides of the border.

“That’s how you get a million people moving northward across the border every day,” he said. “We don’t know exactly how many people who come into the US without authorization. Let’s say 400,000 a year. Well, there’s more than 300 million legal northbound crossings in a year. That’s a ratio something on the order of 1,000 to one.”