We can understand the reasons why both inflation and deflation are damaging. But why is the target ~2% for which there seems some international consensus, rather than 0%.
Is it because consequential behaviours are not balanced - behaviours will tend to change progressively under increasing levels of inflation, but deflation at any level initiates an immediate behavioural change. Deflation:
- reduces spending in the expectation that prices will fall - very directly reduces employment and economic growth
- saving, not enterprise, is the basis upon which wealth is accumulated
- asset values (eg: property) tend to fall - their value rests upon their demand
- makes it difficult to repay existing loans or act as security for new borrowing.
- theoretically leads to negative interest rates which encourages money under the mattress rather than in the bank
There is a very different emotional response to interest rates which are used as the principal economic control lever and impacts the balance between spending, investment and saving. So it is probably better to target inflation at between (say) 1% and 3%, rather than -1 to +1%.