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| Håvard Hungnes, Terje Skjerpen, Jørn Ivar Hamre and Xiaoming Chen Jansen |
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| ''Implications of not controlling for known events in seasonal adjustment'' |
| ( 2024, Vol. 44 No.3 ) |
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| Seasonal patterns in time series can change due to important events, such as legislative changes. If not taken into account, seasonal adjustment can produce misleading results. Two legal changes in Norway in 2022 and 2023 boosted house prices at the start of the year. If no adjustment is made for this, an enhanced seasonal pattern appears, which implies a slight increase in house prices in late 2023. This prompted the Norwegian central bank to raise the key interest rate in December 2023. But house prices adjusted for the legislative changes actually show a decline in the second half of 2023. |
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| Keywords: Outliers, X11, ARIMA, Seasonal filters, House prices, Legislative changes |
JEL: C2 - Single Equation Models; Single Variables: General
C8 - Data Collection and Data Estimation Methodology; Computer Programs: General |
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| Manuscript Received : Feb 19 2024 | | Manuscript Accepted : Sep 30 2024 |
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