A more granular approach to lockdowns
Christian Gollier uses a multi-risk SIR model (MR-SIR) where infection, hospitalization and fatality rates vary between groups. He models two polar solutions, one with strong restrictions with the objective to crush the curve as soon as possible, and another one with much milder restrictions just to flatten the curve. His results suggest:
- The suppression strategy necessitates confining 90% of the entire population for 125 days, while he flatten-the-curve strategy imposes the confinement of 30% of the entire population for six months, followed by almost a year of a low level of the virus prevalence in the population. These two very different strategies yields a similar total cost around 15% of annual GDP;
- Switching from crush-the-curve to the flatten-the-curve strategy a few days short of the 125 days dramatically increases the total cost of the pandemic, which increases from 15% of annual GDP to around 24%, because of the second wave of infection that this switch in policy generates;
- As seniors are much more vulnerable, a simple recommendation would be to shelter them as one deconfines young and middle-aged people in order to build collective herd immunity.
Cost-benefit analysis of age-specific deconfinement strategies
Authors: Christian Gollier
From: Toulouse School of Economics
What is the optimal policy?
Acemoglu and al. also use a a multi-risk SIR model (MR-SIR) to compare between three optimal policies:
- Optimal uniform policies, where the same lockdown is applied to all three age groups;
- Optimal semi-targeted policies, where the oldest group, which has no economic contribution, has a strict lockdown while the other two groups experience a less severe and shorter lockdown;
- Optimal fully-targeted policies, where: a) the youngest group has a very limited lockdown, starting with only 30% of their cohort being subjected to lockdown and with these restrictions being lifted very rapidly; b) the middle-aged group experiences a more extensive lockdown than under the semi-targeted policy, and c) the oldest group is under strict lockdown.
The main message from their baseline results is that targeting has a major benefit in terms of both lives saved and reduced economic damage relative to optimal uniform policies, and interestingly, most of this benefit can be achieved with the semi-targeted policies.
A Multi-Risk SIR Model with Optimally Targeted Lockdown
Authors: Daron Acemoglu, Victor Chernozhukov, Iván Werning, Michael D. Whinston
From: MIT
