最適解は高齢者限定のロックダウン

Kohei Kawaguchi=Sunada @mixingale

使いやすそうなモデル "Targeted policies that are combined with measures that reduce interactions between groups and increase testing and isolation of the infected can minimize both economic losses and deaths in our model"　nber.org/papers/w27102?…

rionaoki @rionaoki

高齢者により厳しいロックダウンを課すことで、同じコストでより多くの命を救えるという極めて直感的な結果。

Ivan Werning @IvanWerning

Just finished this research with Daron Acemoglu, Victor Chernozhukov & Mike Whinston (I know, lucky for such an awesome eclectic team!) I'm exhausted from many late-night meetings, after kids in bed, so happy to see it out. nber.org/papers/w27102.… Let me explain it a bit. 1/n pic.twitter.com/fWFN4EAhpq

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Ivan Werning @IvanWerning

Where to start? COVID-19 has one incredibly striking feature. Its severity varies strongly with age, hitting the elderly hard, but sparing most of the young. We are talking ORDERS of MAGNITUDE. Estimates vary, but there is much agreement on this. 2/n

Ivan Werning @IvanWerning

For example, Fergurson's numbers for mortality 0.1% 20-49 1% 50-64 6% 65+ You can find different and lower numbers, but the pattern is similar. To us these are facts to grapple with, not to be ignored. 3/n

Ivan Werning @IvanWerning

Before I continue, let me leave this here. An online tool to visualize and experiment with possible responses to the epidemic within our model. mr-sir.herokuapp.com/main (Big shoutout to MIT's Rebekah Dix who created this!) 4/n

Ivan Werning @IvanWerning

We take a standard SIR epidemic model and add multiple risk groups (MR-SIR for short). The typical SIR model you may see out there has just one group, but epidemiologists have such extensions. What we add to this: we studying optimal lockdown policy in this framework. 5/n

Ivan Werning @IvanWerning

In particular, we study policies that target different risk groups differently. Our point: finer policy lever can help you save lives AND lower economic losses. This diagram illustrates that. pic.twitter.com/UT2isclBjb

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Ivan Werning @IvanWerning

Important disclaimer: even within the model there is a lot of uncertainty on parameters (we consider a range around a baseline). But it is a crucial weakness of any study of this kind. However, we think the greater point that there are gains to targeted policies is robust. 7/n

Ivan Werning @IvanWerning

Our MR-SIR model looks like this. Groups interact, and get sick, but have different mortality. 8/n pic.twitter.com/AGq7Zjuq3i

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Ivan Werning @IvanWerning

After parameterizing the model the best we could (comments welcome) we put this model through our Optimal Control of lockdown policies, both over time and across groups. This is what we get for the frontier. pic.twitter.com/NpKxHJ7LRn

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Ivan Werning @IvanWerning

I like to emphasize the frontier rather than a particular point or policy. Picking a point on the frontier requires picking a very tricky and controversial parameter: the Value of a Statistical Life (VSL). Different points on this frontier correspond to different VSL.

Ivan Werning @IvanWerning

Some believe setting a VSL has ethical problems, but it is also just notoriously difficult to agree on this parameter! How can you use our frontier or others like it then? 11/n

Ivan Werning @IvanWerning

Say current policy, determined somehow by society or politics, is putting us on some point of the upper frontier. Then you can offer alternatives on the lower frontier that are better, saving more lives and reducing economic activity. 12/n

Ivan Werning @IvanWerning

We find is that the most important distinction is separating the elderly (O for old) from the young (Y) and middle (M) aged. According to our parameters, targeting Y and M separately has marginal gains only. Semi-targeting is almost as good as full targeting. 13/n

Ivan Werning @IvanWerning

Just as an example, here is a point on the frontier and its policies. Comparing non-targeted with semi-targeted. 14/n pic.twitter.com/OXuq4XWPIf

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Ivan Werning @IvanWerning

Note: we assume lockdowns are imperfect, only 75% effective, an important parameter in our model, also that mortality rises with hospital use. We can also feed in different private social distancing efforts, we are looking for evidence on how these translate into beta. 15/n

Ivan Werning @IvanWerning

Next, we add in other policies to the mix. Test-trace-and-isolate, but also what we call group-social distancing.

Ivan Werning @IvanWerning

Our model includes a parameter for the fraction of infected that get isolated. Testing increases this fraction. We find this is a very powerful tool, confirming many experts voicing this recommendation. But targeting lockdown is still very helpful. 17/n pic.twitter.com/XUuGG7bmIf

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Ivan Werning @IvanWerning

Combining targeting with testing should be especially useful in situations with scarce testing resources, which we are currently working on. That figure is from the online GUI I mentioned earlier, the third tab here mr-sir.herokuapp.com/main 18/n

Ivan Werning @IvanWerning

We also look at Group Distancing. People interact more with their own age groups and infections are predominantly from within age groups. As in this figure from here rivm.nl/en/novel-coron… pic.twitter.com/R0Pa2kYU8S

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Ivan Werning @IvanWerning

Policies to discourage against avoidable contacts across groups increase Group Distancing and we show this is very valuable. Indeed, combined with testing, in our model it is a silver bullet of sorts. Again, a figure from the 3rd tab of the GUI: pic.twitter.com/TRYlRc9Nwx

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高田映一 🌗 @takadaeiichi

ダロン・アセモグルMIT教授の致死率の高い65歳以上を隔離してそれ以外は早期に経済活動を再開する政策が社会的最適という論文。 twitter.com/IvanWerning/st… twitter.com/ikedanob/statu…

池田信夫 @ikedanob

何も被害がないのに「鎖国」して国民を貧困に突き落としたニュージーランドは、コロナ騒ぎの「負け組」。台湾もシンガポールも出口がない。 twitter.com/takadaeiichi/s…

2020-05-04 17:05:12

Rui (rhwtsh) @rhwtsh

こりゃすげえの来た。でも素人考えでも、だいぶ前からずっとこれを待ち望んでた。こういう議論を歓迎しないorここまで示唆もしなかった「専門家」への不信は、今後どんどん深刻なものになると思う。不信感の拡散をがんばってmitigateしない限り。当事者やお仲間での自己正当化はたぶん逆効果。 twitter.com/IvanWerning/st…

Masayo Takahashi @masayomasayo

ロックダウンの仕方の議論は今皆求めているところ。これは年齢による仕分けが効果的と言う計算。 でも、問題が。誰が高齢者の面倒見るの？とも書いてある。 理論と現実の施政は違う。 でもどこまで考えてるのか考えてないのかがわからないのが困りますね。 twitter.com/rhwtsh/status/…