After entering the 2000s, the downward pressure was compounded by a new shock of a declining labor force, and this has been putting further downward pressure on the economy. However, deflation ought not to continue if a central bank is able to sufficiently lower nominal interest rates in the face of such large shocks.
In this regard, the critically important factor is whether a central bank faces the zero lower bound or not. Chart 1, which I borrowed from a paper by President Bullard of the Federal Reserve Bank of St. Louis, shows this in a simplistic manner.