The partial government shutdown is now in its 21st day, with efforts to reopen stymied by Democrats' and Republicans' disagreement over whether to allot $5.7 billion to the construction of physical barriers at the United States–Mexico border. Among President Donald Trump's explanations for a wall: It will slow the flow of drugs into the U.S. and prevent some of the tens of thousands of overdose deaths the country suffers every year.

But is a wall really an effective defense against the drug trade?

Reporting from Pacific Standard and other organizations suggests no. As Trump correctly suggests, Mexico is the immediate previous stop for most of the illicit drugs that enter America. But traffickers don't tend to send their products over the border along the places where Trump would build a wall, as Pacific Standard's Jack Herrera previously reported.