Around the world, in countries afflicted with the coronavirus, stores are sold out of toilet paper. There have been shortages in Hong Kong, Australia, the United Kingdom, and the United States. And we all know who to blame: hoarders and panic-buyers.

Well, not so fast.

Story after story explains the toilet paper outages as a sort of fluke of consumer irrationality. Unlike hand sanitizer, N95 masks, or hospital ventilators, they note, toilet paper serves no special function in a pandemic. Toilet paper manufacturers are cranking out the same supply as always. And it’s not like people are using the bathroom more often, right?

U.S. Health Secretary Alex Azar summed up the paradox in a March 13 New York Times story: “Toilet paper is not an effective way to prevent getting the coronavirus, but they’re selling out.” The president of a paper manufacturer offered the consensus explanation: “You are not using more of it. You are just filling up your closet with it.”

Faced with this mystifying phenomenon, media outlets have turned to psychologists to explain why people are cramming their shelves with a household good that has nothing to do with the pandemic. Read the coverage and you’ll encounter all sorts of fascinating concepts, from “zero risk bias” to “anticipatory anxiety.” It’s “driven by fear” and a “herd mentality,” the BBC scolded. The libertarian Mises Institute took the opportunity to blame anti-gouging laws. The Atlantic published a short documentary harking back to the great toilet paper scare of 1973, which was driven by misinformation.

Most outlets agreed that the spike in demand would be short-lived, subsiding as soon as the hoarders were satiated.

No doubt there’s been some panic-buying, particularly once photos of empty store shelves began circulating on social media. There have also been a handful of documented cases of true hoarding. But you don’t need to assume that most consumers are greedy or irrational to understand how coronavirus would spur a surge in demand. And you can stop wondering where in the world people are storing all that Quilted Northern.

There’s another, entirely logical explanation for why stores have run out of toilet paper — one that has gone oddly overlooked in the vast majority of media coverage. It has nothing to do with psychology and everything to do with supply chains. It helps to explain why stores are still having trouble keeping it in stock, weeks after they started limiting how many a customer could purchase.

In short, the toilet paper industry is split into two, largely separate markets: commercial and consumer. The pandemic has shifted the lion’s share of demand to the latter. People actually do need to buy significantly more toilet paper during the pandemic — not because they’re making more trips to the bathroom, but because they’re making more of them at home. With some 75% of the U.S. population under stay-at-home orders, Americans are no longer using the restrooms at their workplace, in schools, at restaurants, at hotels, or in airports.

Georgia-Pacific, a leading toilet paper manufacturer based in Atlanta, estimates that the average household will use 40% more toilet paper than usual if all of its members are staying home around the clock. That’s a huge leap in demand for a product whose supply chain is predicated on the assumption that demand is essentially constant. It’s one that won’t fully subside even when people stop hoarding or panic-buying.