By reacting late instead of early, economic and public health policies give rise to needless cyclical fluctuations

We examine the behaviour of a system that reacts with a lag to a control variable. We look at the example s of : The economic and financial equilibrium, which reacts with a lag to monetary policy; The public health situation, which reacts with a lag to public health restrictions (curfew, lockdown, etc.); We then know that: The control variable must be used early, with a view to future developments in the economic system it controls; If this is not done and action is delayed, then the control variable must be used much more drastically and the result is cycles, i.e. needless variability in the economic system that is controlled.