Anthony Fauci has admitted to flip-flopping on mask-wearing guidance. Well, not exactly.

On Sunday, MSNBC host Mehdi Hasan replayed a 60 Minutes clip from March 8, 2020, in which the National Institute of Allergy and Infectious Diseases director said, “Right now in the United States, people should not be walking around with masks.” Asked whether he was wrong back then, especially given the Chinese and South Koreans were already wearing masks, Fauci actually offered a spirited defense of his ultimate U‑turn, alluding to the famous dictum that “when the facts change, I change my mind.”

In Fauci’s eyes, the knowledge base last spring justified his opposition to mask-wearing in the community. First, there was a lack of evidence that masks actually worked in reducing transmission of the virus back then, he said, at least outside of hospital settings. Second, public health officials also thought asymptomatic or presymptomatic transmission of the virus was rare.

If the virus was only spread by those coughing or with fevers, most of whom would be isolating at home or in the hospital, then community-wide face coverings would be pretty useless. It was only when it became clearer masks did help and that presymptomatic and asymptomatic spread was common, Fauci said, that it made sense to encourage people to wear them when necessary.

At least, that’s the official line. But there’s an obvious problem with Fauci’s reasoning here. An absence of evidence of masks’ effectiveness and hunches about how the virus spread might have justified warning the public that masks were no silver bullet or, indeed, that their voluntary use should not be seen as a substitute for social distancing. But given masks were an extremely low-cost means of potentially mitigating risk for individuals, the risk-to-benefit ratio was clearly favoring permissive guidance on their use.

“The science,” in other words, never justified Fauci telling people specifically not to wear masks, rather than remaining neutral. That harder opposition ultimately came because of Fauci’s third argument — that a failure to dissuade people from wearing them back then would have exacerbated mask shortages, leaving healthcare workers without access to crucial personal protective equipment.

The key reason for Fauci and Surgeon General Jerome Adams discouraging mask-wearing therefore had little to do with science. It stemmed from both playing armchair economists. Yet, their economics was faulty. Mask markets are not, and would never be, static and zero-sum — with rising demand from the public “using up” masks meant for healthcare workers.

Provided politicians didn’t interfere too much with price rises, suppliers would have quickly ramped up production or entered the sector for surgical mask production, as we eventually saw. The belief that mask-wearing was beneficial coupled with rising prices would have led to smaller-scale innovation too (not least people making cloth masks at home) or finding other means of protection in the interim.

Yes, it’s difficult to look at the recent waves here and abroad despite high self-reported mask-wearing and conclude that masks are so effective that government mask mandates deserved central billing, as in Joe Biden’s presidential campaign. So, Fauci’s error can’t be held up as one of the crucial drivers of the early U.S. death toll.

But that early guidance almost certainly led to lower voluntary mask-wearing than we would otherwise have seen in those early months, worsening community transmission of the virus somewhat on the margin. What’s more, the subsequent change of heart from Fauci and Adams made even voluntary mask-wearing a much more politically charged issue than it needed to be.

At the end of the case for his defense, Fauci defined flip-flopping as a situation in which one alters his position without the underlying data changing. What happened with masks, he said, was that his stance evolved simply because new evidence materialized. This was science in action.

But the pertinent underlying fact that defined Fauci’s position was not the scientific uncertainty, but a judgment on how economic markets operated. Any good economist would have told Fauci that his pessimism there was misguided. As with so many other errors during this crisis, lift the lid on a public health mistake, and you find, undergirding it, an error of economic reasoning.