
A Multi-Risk Sir Model with Optimally Targeted Lockdown [pdf] - Isamu
https://economics.mit.edu/files/19699
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Isamu
> We develop a multi-risk SIR model (MR-SIR) where infection, hospitalization
> and fatality rates vary between groups—in particular between the “young”,
> “the middle- aged” and the “old”. Our MR-SIR model enables a tractable
> quantitative analysis of optimal policy similar to those already developed
> in the context of the homogeneous- agent SIR models. For baseline parameter
> values for the COVID-19 pandemic applied to the US, we find that optimal
> policies differentially targeting risk/age groups sig- nificantly outperform
> optimal uniform policies and most of the gains can be realized by having
> stricter lockdown policies on the oldest group. For example, for the same
> economic cost (24.3% decline in GDP), optimal semi–targeted or fully-
> targeted poli- cies reduce mortality from 1.83% to 0.71% (thus, saving 2.7
> million lives) relative to optimal uniform policies. Intuitively, a strict
> and long lockdown for the most vulnera- ble group both reduces infections
> and enables less strict lockdowns for the lower-risk groups. We also study
> the impacts of social distancing, the matching technology, the expected
> arrival time of a vaccine, and testing with or without tracing on optimal
> policies. Overall, targeted policies that are combined with measures that
> reduce inter- actions between groups and increase testing and isolation of
> the infected can minimize both economic losses and deaths in our model.

