Note the time scale

Figure 1 Inflation in currency unions 
under behavioural expectations (top) 
and rational expectations (bottom)

This is a graph from learning behavior and central banking.

It takes 15 years for  100 million traders to get a clue.  If we could get a clue every 6 years economic life would be a bit smoother.
Getting a clue is called 'marking to market', and in government circles it means the one generation doing some serious overlapping with the other.