Information Note – Rebase of Industrial Production and Turnover (IPT) Index Base (2021=100)

CSO, 09 December 2024, 11am

The CSO’s Industrial Production and Turnover (IPT) Index for October 2024 was published on 09 December 2024. These indices have been compiled for the first time with the reference to base year 2021=100 as per Eurostat Regulation.

Background – Index Calculation

Individual turnover sub-indices are compiled for each detailed NACE class (i.e. NACE 4-digit level). These sub-indices are combined to provide the indices for broader sectoral groupings (NACE 2-digit and groupings of NACE) using the turnover as the weight. The production indices are created in the same way but use the gross value added at factor cost (GVA) as the weight. The production indices are calculated at constant prices, using the Wholesale Price Index (Base 2021=100) as deflators. The base-year GVA and turnover weights are from the 2021 Census of Industrial Production (CIP). The weights and base year are usually updated every five years. 

Scope of Changes due to IPT Rebase

Changes to the data as part of the 2021 series rebase process for the Industrial Production and Turnover Indices are outlined in Table 1.

Table 1: Changes as part of rebase to the Industrial Production and Turnover Indices
	Change	Action
Revisions to the raw data	Specific identified changes to the raw data due to new or updated information.	The identified changes were included in the calculation of both the Turnover and Production indices.
Changes to weights	As part of the rebase, the weights have been updated using the 2021 Census of Industrial Production.	New weights are applied to all indices and aggregates from 2021 onwards.
Wholesale Price Index (WPI) deflator	As part of the rebase process, a new set of deflators were derived from the Producer Price Index (PPI), as part of the WPI release, which was itself rebased to 2021=100. For details on the methodology see Introduction of Updated PPI/WPI series (base year 2021=100) [1].	New PPI deflator implemented to calculate the Industrial Production Index series from Jan 2021. (Industrial Turnover indices are not deflated).
Updating of the Seasonal Adjustment Modelling	Due to the above changes in the data series, the seasonal adjustment modelling has been updated.	A review of the Seasonal Adjustment approach was concluded, and the decision was made to continue with the Direct approach.[2] The seasonal adjustment modelling has been updated to include changes to data as part of rebase.

[1] Introduction of Updated PPI/WPI Series (Base year 2021=100) 

[2] Industrial Production and Turnover Seasonal Adjustment Review

Impact of the Series

Figure 1 illustrates the impact of the changes between the 2021 series and the rescaled 2015 series as part of the rebase process on the Unadjusted Production in Manufacturing Industries from January 2015.

Figure 2 presents the effect of the changes between the rebased 2021 series and the rescaled 2015 series on the Unadjusted Production in Manufacturing Industries from January 2015.