seasonal index

Otherwise, the 12 monthly averages will be considered as seasonal indices.

To initialize the seasonal indices "c" there must be at least one complete cycle in the data.

This implies that if monthly data are considered there are 12 separate seasonal indices, one for each month.

Let us calculate the seasonal index by the ratio-to-moving average method from the following data:

Seasonal variation is measured in terms of an index, called a seasonal index.

The following methods use seasonal indices to measure seasonal variations of a time-series data.

Each seasonal average is multiplied by the correction factor 1.3371 to get the adjusted seasonal indices as shown in the above table.

The method calculates a trend line for the data as well as seasonal indices that weight the values in the trend line based on where that time point falls in the cycle of length "L".

Revised Seasonal Indexes UPDATED Each year with the release of the January CPI, seasonal adjustment factors are recalculated to reflect price movements from the just-completed calendar year.