Le confinement optimal : quelques calculs exploratoires

Is it possible to explain or to « rationalize » the Great Lockdown, that is, the strict lockdown strategy implemented against the Covid-19 pandemic around the world in the year 2020? This article proposes to re-examine the normative foundations of lockdown policies in the presence of a pandemic. For that purpose, we analyse different social welfare criteria, which can be used to assess the optimal degree of lockdown under a pandemic, and we compare the solutions of those social planning problems. We show that each of those social welfare criteria provides a particular treatment of the trade-off between saving human lives and promoting prosperity. Whereas the utilitarian criterion and the majority rule (in the presence of altruism towards the old) tend, under weak conditions, to legitimate a strict lockdown, ex post egalitarianism (which gives absolute priority to the worst-off in realized terms) and the majority rule (in the absence of altruism) rationalize a minimum lockdown. The optimal strength of the lockdown is thus shown to lack robustness with respect to the pursued social welfare criterion.