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Seasonal adjustment
Definition
The development of a statistical series may in general be broken down into three factors: a trend, a seasonal component and an irregular component. Seasonal adjustment is a technique that statisticians use to eliminate the effect of normal seasonal fluctuations on data, so as to bring out fundamental trends (trend and irregular component).
For example, the seasonally adjusted unemployment rate eliminates variations due to the seasonal habit of hiring in the summer and dismissing in the winter in business sectors such as agriculture and the building industry.
