Concerning the desirable level of (properly measured) inflation, there seems to be a consensus that a low positive number (1-3%) is better than zero.1 The reasons for this are both a priori and empirical.
When inflation averages zero over time, the price level must, by definition, be falling for a significant part of the time (and a significant number of individual prices will be falling, even if the general price level is flat). This creates two problems.