The Case against Lockdowns

Summary

• A year ago, when the COVID-19 pandemic hit most of the world, there was arguably a good case for lockdowns. The initial growth of the epidemic implied a high basic reproduction number, which in turn meant that unless transmission was reduced the virus would quickly sweep through most of the population because incidence would continue to grow exponentially until the herd immunity threshold was reached, overwhelming hospitals and resulting in the deaths of millions of people in a few weeks. Lockdowns and other stringent restrictions seemed like a plausible way of reducing transmission to "flatten the curve" and prevent that scenario from materializing.

• Many people continue to reason along those lines, but since then we have learned that, whatever the precise effect that lockdowns and other stringent restrictions have, it is not so large that it can easily be picked up in the data, as it would surely be if restrictions had the very large effect that pro-lockdown advocates claim. In particular, it is not the case that the alternative to lockdowns is herd immunity (at least in the short run), because in practice incidence never grows exponentially for very long even in the absence of stringent restrictions. While it is plausible that, without stringent restrictions, incidence would start falling a bit sooner and faster, the data show very clearly that it always starts falling long before the herd immunity threshold is reached with or without a lockdown.

• Many factors likely contribute, but the main explanation of that fact is probably that, despite what simple epidemiological models assume, people modify their behavior in response to changes in epidemic conditions such as rising hospitalizations and deaths, which reduces transmission and causes the epidemic to recede long before the herd immunity threshold is reached. However, until enough people have acquired immunity through natural infection or vaccination, this is only temporary and eventually incidence starts growing again because people go back to more regular behavior. Lockdowns and other stringent restrictions do not have a very large effect because they are a blunt instrument and have a hard time targeting the behaviors that contribute most to transmission.

• The belief that lockdowns are very effective nevertheless persists because authorities react to the same changes in epidemic conditions as the population, so they tend to implement lockdowns and other stringent restrictions around the time when people start modifying their behavior. This means that the effect of voluntary behavioral changes is attributed to lockdowns even if the epidemic would have started to recede in the absence of stringent restrictions. We know this because that is exactly what happened in places where the authorities did not put in place such restrictions, which are extremely diverse economically, culturally and geographically and therefore unlikely to share some characteristics that allow them to reduce transmission without a lockdown.

• Places where the virus seems to have spread more are those where the population is relatively young, which is exactly what the theory presented here–that voluntary behavioral changes in response to changes in epidemic conditions are the main driver of the epidemic–predicts, since a younger population implies a lower rate of hospitalization and death, which in turn means that the virus will have time to spread more before the rise in hospitalizations and deaths scare people into changing their behavior enough to push the reproduction number below 1.

• The scientific literature on the effect of restrictions on transmission contains many inconsistent results, but more importantly it is methodologically weak and therefore completely unreliable. To be sure, many studies found that restrictions had a very large effect on transmission, which pro-lockdown advocates like to cite. However, those results do not pass a basic smell test since one just has to eyeball a few graphs to convince oneself the studies they come from perform terribly out of sample, which is not surprising since most of them either assume that voluntary behavior has no effect whatsoever on transmission or do not use methods that can establish causality by disentangling the effect of restrictions from that of voluntary behavior changes.

• Even if you make completely implausible assumptions about the effect of restrictions on transmission, and ignore all their costs except their immediate effect on people's well-being, they do not pass a cost-benefit test. For instance, in the case of Sweden (where incidence is growing again and the government is considering tightening restrictions), if you assume that a lockdown would save 5,000 lives (which is approximately the total number of deaths during the first wave, when the population was behaviorally naive and vaccination was not under way), a 2-month lockdown followed by a gradual reopening over the next 2 months would have to reduce people's well-being by at most ~1.1% on average over the next 4 months in order to pass a cost-benefit. In other words, for a lockdown to pass a cost-benefit test under those assumptions, you would have to assume that on average people in Sweden would not be willing to sacrifice more than ~32 hours in the next 4 months to continue to live the semi-normal life they currently enjoy instead of being locked down.

• While I use Sweden to illustrate my point because it has been a focal point of the debate about restrictions, this exercise yields a similar conclusion almost everywhere else. The truth is that, from a cost-benefit perspective, Sweden's much-decried strategy has been vastly superior to what most Western countries have done and it is not even close. Even if you think that it would have been better for Europe and the US to follow Australia and New Zealand's example by adopting a so-called "zero COVID" strategy after the first wave, which would probably not have succeeded anyway even back then, this boat has already sailed and trying to pull it off now makes absolutely no sense from a cost-benefit perspective. Despite popular but confused arguments to the contrary, which I discuss at the end of this essay, this remains true even if you take into account the threat posed by new variants of SARS-CoV-2.

Almost every country in the world has now gone through 2 or 3 waves of the COVID-19 pandemic and, in most of them, incidence remains high although it has recently been falling almost everywhere. everywhere. Although the vaccine is being rolled out in many places, it is at a very slow pace with most countries facing shortage and distribution problems. This means another flare-up is likely in many places even if the worst of the pandemic is probably behind us. While lockdowns and other stringent restrictions had high levels of support when the first wave hit, this is no longer true and, as we are entering the last phase of the pandemic, the debate about how to deal with it has never been so intense. Sweden went a different route last spring by foregoing a lockdown and, while it remains widely vilified for this decision, even some people who thought it was a mistake at the time have changed their mind and now think other countries should follow Sweden’s example and seek to contain the epidemic without stringent restrictions such as stay-at-home orders, outright business closures, etc.

I’m one of them. Back in spring, I was in favor of lockdowns, but since then I have reached the conclusion that lockdowns and other stringent restrictions do not make sense from a cost-benefit perspective. I now think that, even with the information we had at the time, supporting lockdowns was the wrong call because even though I insisted that it was only a temporary solution and that we should be ready to revise our view as more evidence came in, I should have known that people would not and that lockdowns would quickly become institutionalized. However, in this post, I will not be arguing for this view. I only want to argue that, regardless of what should have been done last spring, the data we have accumulated since then show very clearly that, whatever the precise effect of lockdowns and other stringent restrictions, it is not nearly as large as we might have thought, so their costs far outweigh their benefits and we therefore should avoid them where they are not currently in place and start lifting them immediately where they are.

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