Identifying Changes in Mean, Seasonality, Persistence and Volatility for G7 and Euro Area Inflation

This study examines the properties of monthly CPI inflation in G7 countries and the Euro area (aggregate) over the period 1973-2007 using a new iterative decomposition procedure that separates changes in mean, seasonal and dynamic components together with conditional volatility. We uncover mean and seasonality breaks for all countries and, even allowing for these, changes in persistence are indicated for all countries except Canada. Further, while volatility reductions are widespread in the mid- to early 1980s, Canada, France and the US all exhibit increased volatility from 1999 onwards. Of methodological interest, iteration is shown to provide more evidence of persistence breaks and fewer volatility breaks overall compared with the usual approach of sequentially examining changes in the properties of inflation, while application of linear seasonal adjustment also reduces evidence of persistence breaks. Although failure to allow for breaks in mean, seasonal or dynamic components affects conclusions about the existence and dates of volatility breaks, nevertheless, evidence remains of a volatility increase in some countries in 1999.