There are a couple of central banks (RBA, Federal reserve for example) that use inflation rate as a key indicator to regulate their official cash rates.
Those target inflation rates usually range from 2%-3%.
This is taken from federal reserve's official website:
Over time, a higher inflation rate would reduce the public's ability to make accurate longer-term economic and financial decisions. On the other hand, a lower inflation rate would be associated with an elevated probability of falling into deflation
World has changed in the past 10 years or so:
World's prevailing overnight cash rates have plunged from 3%-20% in the 20th century to 0%-3% in the past 5 years.
So is there any scientific proof that 2% inflation rate (or 2%-3% in RBA's case), is still the optimum target in today's low interest rate regime?