Their paper is a prime example of propaganda masquerading as science that weaponizes complicated mathematics to promote questionable policies

From Lockdowns, science and voodoo magic by Philippe Lemoine.  He is addressing the model weaknesses which undermine a key paper supporting lockdowns.

As Europe and the United States are experiencing a second or third wave of the pandemic, depending on how you count, the debate about lockdowns is raging again. Many people are convinced they are the best way to deal with the pandemic until a vaccine arrives. Back in the Spring, I argued in favor of lockdowns because we didn’t know much about the virus and Western governments were caught by surprise (I’m not even sure I was right anymore, even when you don’t look at things in retrospect with the information we now have, but that’s a question for another day), but now I think we should not resort to them anymore. The main reason is that, after looking at the data we have accumulated in the past few months, I have come to believe that lockdowns weren’t as effective as most people think relative to less stringent restrictions. People seem to believe that lockdowns are the only kind of policy that can prevent a colossal loss of life, because less stringent restrictions just don’t cut transmission enough. They also say a lot of things about lockdowns, especially about their effects on the economy, which I think are false, but in this post I want to focus on the claim that only lockdowns are really effective to cut transmission and ultimately prevent a lot of people from dying.

Whenever someone makes that claim, you can be certain they will cite the paper Flaxman et al. published in Nature a few months ago, which concluded that non-pharmaceutical interventions had saved more than 3 millions lives in Europe in the Spring and that among those interventions only lockdowns had a substantial effect. This paper went viral when it was published and continues to be cited all the time as proof that lockdowns saved countless lives during the first wave. This isn’t just true in informal discussions, but also in the scientific literature, where this paper is systematically cited to support the claim that lockdowns are very effective. (It’s already been cited almost 450 times since it was published a few months ago.) I hadn’t read it until very recently, but since the debate about lockdown has been rekindled by the second wave in Europe, I decided to read it and I was astonished by how bad it was. Since it still plays a very important role in that debate, I think it’s important to explain why it’s bad, so in this post I’m going to take it apart and explain why even Flaxman et al.’s own analysis shows that, while lockdowns do make a difference, they don’t cut transmission that much more than other, less stringent and therefore less costly restrictions. (I basically taught myself Stan over a weekend to do this, so someone should probably check my code, though I’m pretty sure there are no major mistakes.) After pointing out that it changes the policy debate quite a lot, I conclude with a few remarks about the role bad science has played in this debate and how this paper illustrates why the cult of science that many people have fallen into is bad.

He then goes through the many weaknesses of the model in careful detail.  It basically comes down to the authors of the model having made a range of assumptions, many of them unsupported by evidence, that virtually assured that the model would find that lockdowns are effective.

He concludes:

I have no doubt that lockdowns saved lives, but they didn’t save nearly as many as people think and they certainly didn’t save 3 million lives in Europe alone during the first wave, as Flaxman et al. claim. They use sophisticated statistical techniques to reach a conclusion that can be rejected with a high degree of certainty just by eyeballing a chart. Their paper is a prime example of propaganda masquerading as science that weaponizes complicated mathematics to promote questionable policies. Complicated mathematics always impresses people because they don’t understand it and it makes the analysis look scientific, but often it’s used to launder totally implausible assumptions, which anyone could recognize as such if they were stated in plain language. I think it’s exactly what happened with Flaxman et al.’s paper, which has been used as a cudgel to defend lockdowns, even though it has no practical relevance whatsoever. The truth is that, with the data and methods they used, it’s impossible to estimate the effect of non-pharmaceutical interventions and anyone who claims otherwise is selling snake oil.

"Their paper is a prime example of propaganda masquerading as science that weaponizes complicated mathematics to promote questionable policies."  There is a lot of that going around today.