Definitions and explanations
The Activity Index (AI) measures activity in the economy. It is a regression model with the following explanatory variables: Industrial production index, Hours worked by employees in government agencies, Turnover in retail trade, and Exports and imports of goods.
The Activity Index exists in three variations: the original series, the seasonally adjusted series and an estimation of the trend. The trend reduces the effect of temporary disturbances in the seasonally adjusted index.
The Activity Index, original series, is calibrated to the non-adjusted GDP (2005=100), so that GDP and the Activity Index are equal for all quarters. The average value for the Activity Index original series for the months in the quarter is equal to GDP for the quarter, calculated as an index (2005=100).
Revisions of the Activity Index
When the Activity Index for a new month is published, the index for previous months is also normally revised. This is mainly due to new/revised indata to the Activity Index and how these data interact in the models used. New/revised GDP information also affects the series backwards in time.
Deviation between GDP and Activity Index (Bias)
When GDP for the current quarter is not known, the deviation (bias) between the Activity Index and the most recently published GDP is extrapolated. For example, if a non-adjusted Activity Index is 2 index points higher than the latest GDP (calculated as an index) the Activity Index is reduced by 2 index points.
Certain GDP components are not measured in the Activity Index, such as investments and export/import of services. If these components develop differently than GDP in general, the deviation between the Activity Index and GDP will increase.
Data in current prices in the Activity Index is used for export and import. Significant price changes then result in deviations between the Activity Index and GDP in constant prices.
Deviations (bias) between the non-adjusted Activity Index and GDP is reported in a separate series to be found among Requested tables and graphs. See "Data and graphs for printing out" (xls).