SEASONALITY

Seasonality is a trait of a time series. If a time series has a seasonality this means that the data behaves in a predictable and expected way in a specific time of year or season. It is a recurring activity for every one-year period. Changes or patterns in the data are called seasonal if they are anticipated to happen in the same time of every calendar year.

Seasonal effects are not the same as cyclical effects as seasonal effects are contained in a yearly cycle while cyclical effects may extend to time periods that are longer or shorter than one calendar year. Examples of cyclical effects are increased sales due to low unemployment rates.