  Various measures have been taken in different countries to mitigate the
Covid-19 epidemic. But, throughout the world, many citizens don't understand
well how these measures are taken and even question the decisions taken by
their government. Should the measures be more (or less) restrictive? Are they
taken for a too long (or too short) period of time? To provide some
quantitative elements of response to these questions, we consider the
well-known SEIR model for the Covid-19 epidemic propagation and propose a
pragmatic model of the government decision-making operation. Although simple
and obviously improvable, the proposed model allows us to study the tradeoff
between health and economic aspects in a pragmatic and insightful way. Assuming
a given number of phases for the epidemic and a desired tradeoff between health
and economic aspects, it is then possible to determine the optimal duration of
each phase and the optimal severity level for each of them. The numerical
analysis is performed for the case of France but the adopted approach can be
applied to any country. One of the takeaway messages of this analysis is that
being able to implement the optimal 4-phase epidemic management strategy in
France would have led to 1.05 million infected people and a GDP loss of 231
billion euro instead of 6.88 million of infected and a loss of 241 billion
euro. This indicates that, seen from the proposed model perspective, the
effectively implemented epidemic management strategy is good economically,
whereas substantial improvements might have been obtained in terms of health
impact. Our analysis indicates that the lockdown/severe phase should have been
more severe but shorter, and the adjustment phase occurred earlier. Due to the
natural tendency of people to deviate from the official rules, updating
measures every month over the whole epidemic episode seems to be more
appropriate.
