1/7 To characterize a rational exit strategy to #lockdown , we must combine epidemiology with economics.

I am not an epidemiologist, just an economist. Moreover, our date to test our models are very reliable. Beware!

Here is my model: https://www.tse-fr.eu/publications/lockdowns-and-pcr-tests-cost-benefit-analysis-exit-strategies

2/7 Without social distancing, treatment, vaccin and test, herd immunity will require 80% immunization. Getting there would be catastrophic in terms of death toll.

Laisser-faire dynamic of the pandemic in France implies a death rate around 1%.

3/7 Under 80% lockdown, R0 goes down to 0.85 in my model. This is too large. At this rate, it will take 45 weeks of 80% lockdown to eradiquate the virus.

Death rate in population 0.04% and 34% GDP loss under this suppression strategy.

4/7 The political pressure to deconfine will be unbearable soon. But the immunity (prevalence) rate is much too low (large). Second wave of pandemic certain, first this summer, then at Christmas.

Death rate 0.1%, GDP loss 30%. (assuming vaccin available March 2021).

5/7 Long lockdown or stop&go? One cannot decide without giving a value to life/death.

Democratic debate on this is urgent! Assume 1 death = 1 million euros.

Here is the cost-benefit analysis:

6/7 Frankly, none of these policies is politically viable.

Let's dream. Suppose we can test 50% of the population every week, rotating. The negatives are sent back to work for 7 days.

0.02% of the population will die; GDP loss only 8%.

Much better! Where are the tests!?!!

7/7 Remember: The credibility of this analysis is not better than the credibility of the data on which it is based.

Prudence. I will take account of parameter uncertainties in the next version of this work.