WHY DRUG INTERDICTION IS DOOMED TO FAILURE.

• Author: Sullum, Jacob
• Position: DRUGS

"I'M GOING TO create borders," Donald Trump promised while running for president in 2016. "No drugs are coming in. We're gonna build a wall."

Halfway through his term, the president's faith in "the border wall" as a way of blocking the "pipeline for vast quantities of illegal drugs" was unabated, even as spoilsports noted that the supply comes in mainly through legal points of entry, making the wall irrelevant. And if stopping drugs at the southern border is a tall order, the prospect of intercepting them before they get there is even dimmer, as a study published recently in the Proceedings of the National Academy of Sciences demonstrates.

"The U.S. government's own assessments have long showed that interdiction has at best only an ephemeral impact on retail prices and supply," note University of Alabama geographer Nicholas Magliocca and his seven co-authors. "Wholesale cocaine prices in the United States have dropped significantly since 1980, deaths from cocaine overdose are rising, and the dismal rate at which counterdrug forces intercept cocaine shipments is well documented."

Critics cite two major reasons why interdiction fails: Pushing down drug trafficking in one place makes it pop up elsewhere (the "balloon effect"), and the threat of seizures scatters traffickers across a wider area (the "cockroach effect"). Magliocca and his collaborators built a computer model, NarcoLogic, that reproduces these phenomena and predicts cocaine trafficking patterns similar to what actually happened from 2001 to 2014, when the locus of smuggling operations shifted to Central...