COVID-19 and Seasonal Adjustment

Abeln, Barend Jacobs Jan

The COVID-19 crisis has a huge impact on economies all over the world. In this note we compare seasonal adjustments of X13 and CAMPLET before and after the COVID19 crisis. We show results of Quasi Real Time analyses for the quarterly series real GDP and the monthly series Consumption of Households in the Netherlands, and STL and CAMPLET seasonal adjustments for the weekly series US Initial Claims. We find that differences in SA values are generally small and that X13 and STL seasonal adjustments are subject to revision. From the analysis of the weekly series initial claims we learn that STL and CAMPLET SAs follow NSA values closely. In addition, the COVID-19 crisis caused a structural increase in initial claims. Before the crisis initial claims fluctuated around a lower level than after the crisis.