Inflation equals the product of two terms: the fraction of items with price changes (whose volatility figures prominently in state-dependent pricing models), and the average size of those price changes (the only source of fluctuations in time-dependent pricing models). The variance of inflation...

In the 1988-2004 micro data collected by the U.S. Bureau of Labor Statistics for the CPI, price changes are frequent (every 4-7 months, depending on the treatment of sale prices) and large in absolute value (on the order of 10%). The size and timing of price changes varies considerably for a...