A Seasonal Adjustment Principle and a Seasonal Adjustment Method Derived From this Principle

The decomposition of a given time series into trend, seasonal component, and irregular component is formulated as a minimization problem. The trend is chosen such that it is as smooth as possible; the seasonal component is chosen such that it exhibits a seasonal pattern as stable as possible; and the trend and seasonal components are jointly chosen such that the given time series is explained as well as possible by these two components; that is, the irregular component is minimized