Author: Geung-Hee Lee(Korean National Open University), Keunho Jang(Bank of Korea)

 As economic uncertainty grows due to the COVID-19 pandemic, the need to quickly grasp the economic situation is growing. In order to understand the economic situation at an early stage, it is necessary to analyze high frequency data such as daily data rather than the existing monthly and quarterly data. In this study, based on the seasonal adjustment method of Ollech (2018), we prepared a seasonal adjustment method that can be applied to Korean daily data in consideration of national holidays and public holidays. Seasonal adjustments were made by applying this method to daily data of Korea, such as Electricity peak demand, Box office gross, Highway traffic, and Seoul subway ridership. Examining the seasonal adjustment results of the four daily data, it is judged that the seasonal adjustment was appropriate because the seasonally adjusted series was not significant in the seasonal frequency unlike the original series. The seasonally adjusted daily series is found to be more useful than the original series to quickly grasp changes in the economic situation after the COVID-19 pandemic. In the future, it is necessary for the Korean statistics authorities to prepare a pre-processing methodology suitable for Korean daily data by intensifying research on the seasonal adjustment of daily data.