Price index series may be affected by regular seasonal movements which result from sales seasons, vacation practices and similar factors. Often such effects would mask the short-term, underlying movements of the series. By correcting for identifiable seasonality the evaluation of a series may be made more perceptive.
European indices are not seasonally corrected by official compilers. Notice that the ECB perform a indirect adjustment of the main aggregates (ECB (2000)). We seasonally adjust the european indices using the same methodology as is used by the Bureau of Labor Statistics to adjust the CPI for the US (BLS Handbook and homepage).
Below are listed main the main methodological points: