The Seasonal Adjustment Of Monthly CPI

From the reform and opening up to now, the number of our annual data is only over 30 and it’s not enough for many economic studies,so the study of sub- annual time series like quarterly monthly etc. is especially important. The information included in the sub- annual data is effected by the seasonal factor and the dynamic relationship between economic time series becomes blurred due to the interference of seasonal factors. If there is a strong seasonal effect in the time series, the true relationship between them might be masked. Seasonally adjusted data can eliminate the impact of seasonal factors and reflect the real situation of the economy sequences, therefore, the study of seasonal adjustment method of the sub-annual data has important theoretical significance and application value.This paper introduces the background and significance of the CPI seasonal adjustment, and itemizes the previous case study on seasonal adjustment from two angles of home and abroad respectively. On the basis of summarizing research on seasonal adjustment of domestic and foreign scholars, this paper mainly use the X-13A-S model to seasonal adjustment of CPI and the model is the latest results of the U.S. Census Bureau that will be implemented soon. Although there are a lot of literature on the seasonally adjusted, previous studies is not sufficient specific to the latest X-13A-S model.It is needed of more detailed supplementary descendants. First the article introduced X-13A-S model of a detailed theoretical introduction, because X-13A-S includes the function of X-12-ARIMA model and TRAMO-SEATS model and X-13A-S is the inheritance and development of them, the theory introduction also introduces the X-12-ARIMA model and TRAMO-SEATS model. Based on the theoretical description of the X-13A-S model it will be used for the seasonally adjusted of CPI, which will introduce the Spring Festival.After obtaining seasonal adjustment model, the article will use the spectrum to detect their effects. Seasonal and trading day effects is no longer included in the series through the seasonally adjusted from the results of graphs, indicating that the effect of the model is very well. Of course, the process of X-13A-S model for seasonal adjustment is not without any flaws, in the end of this article,the author points out the defects in process of seasonally adjust of the modle, in order to it can be improved by the future researchers. Finally, the article gives some prospects of the seasonal adjustment and also pointed out the goals and direction of the next period of seasonal adjustment.The innovation of this article is mainly reflected in two aspects:First, it’s the first time using the software of Win Genhol to introduce the Spring Festival variable into the model, which provides a reference for the introduction of moving holidays in the future and the software makes it easier to adjust the movig holidays; Second, this article first describes the X-13A-S in detail, then applies it to the seasonal adjustment of monthly CPI, which gets a good effect.