Accurate meaning of seasonal index: seasonal index describes the typical seasonal characteristics of each month or quarter in a year. In the multiplication model, the seasonal index is formed on the condition that its average is equal to 100%, which reflects the size of a month or a quarter in the annual average.

The law of seasonal index is a method to calculate the seasonal variation index that describes the seasonal cycle change in time series. The seasonal index prediction method in statistics is a method to predict the future situation of the predicted object according to the seasonal variation law presented by the data in time series.

Extended data:

1, and the calculation formula of seasonal index is:

Seasonal index (%) = (average/trend value of the same season over the years) *100%; It should be noted that there are two kinds of trend values here: one is horizontal trend and the other is slope trend.

2, the basic idea of seasonal index method:

Firstly, the long-term trend without seasonal fluctuation is separated; Then calculate the seasonal index; Finally, a forecasting model is established. Mathematical model is the product of long-term trend pattern and seasonal index.

Baidu Encyclopedia-Seasonal Index