It is a forecast method, and is to analyze past years' sales performance, price trends, and etc., and to forecast the future change according to the analyzed data. The Time Series Analysis is performed through the following procedure:

1. to illustrate the past time-series data graphically to express its trend line

2. to consider whether the trend line is proper or not

3. to determine the formula and obtain its factor

Time-series data generally consists of four variable elements: Trend, Cycle Movement, Seasonal Variation, and Irregular Component.