Seasonal Adjustment – Consensus between Direct and Indirect Method. Case Study: Seasonal Adjustment of Romanian National Accounts using JDemetra+ 2.1

Abstract :

Regarding the seasonal adjustment of Romanian GDP, there are some inconsistencies between the GDP growth rates computed based on the sum of seasonally adjusted components and the one computed based on the direct seasonal adjustment of the GDP. This paper provides a better understanding of the differences between the direct and indirect method of seasonal adjustment of economic time series and illustrates a possible solution to the problem encountered. Moreover, the seasonal adjustment procedure for TRAMO-SEATS and X13 will be tested using JDemetra+ 2.1. The choice between direct and indirect approach is made taking into account the quality of the seasonally adjusted data, the magnitude of  revisions and consistency between the aggregates and the overall GDP. Although both methods provided satisfactory results, TRAMO-SEATS gave better results with regard to quality and revisions. Some key benefits of choosing the right method are the possibilitily of comparing economic series from month to month and making accurate predictions.