Seasonal adjustment and reliability of euro area GDP – Increased uncertainty in times of unusual developments?

Seasonally adjusted gross domestic product (GDP) data are inevitably surrounded by uncertainty. Disregarding methodological improvements, two main sources of revisions can be distinguished: First, revisions that reflect the incorporation of more comprehensive or more representative, but generally less timely, source data and second, revisions that are related to seasonal adjustment. This paper aims to get some insights into the overall statistical uncertainty surrounding first estimates of quarter-on-quarter seasonally adjusted GDP volume growth in the euro area, in particular the so-called "flash estimate", published by Eurostat around 45 days after the end of the reference quarter, and the first regular estimate, published around two and a half weeks later.