Impact of the Labour Force Survey reweighting on the NI labour market results

The Labour Force Survey has been reweighted to make use of more recent population estimates. Alongside an ONS article on the impact for the UK data series, NISRA have published a paper on the impact for the Northern Ireland data series.

The Labour Force Survey has been reweighted from the January to March 2019 quarter to make use of more recent population estimates, increasing the aged 16 to 64 population in the UK by 484,000 (1.1%) and in NI by 7,000 (0.6%).

As part of this reweighting exercise, ONS uncovered an error in its processing of the NI labour market results.  This error was detected in the previous version of the coding used by ONS for weighting Northern Ireland data, whereby weights were multiplied by a design weight in two separate parts of the code.  The error dates back to the January to March 2020 quarter during the pandemic, when the undetected changes were initially small.  This has now been corrected, resulting in the larger impact of this reweighting exercise on Northern Ireland estimates than for the other countries of the UK.

The key points are as follows:

• The impact of the reweighting to recent periods has been to increase the employment rate and decrease the economic inactivity and unemployment rates.  There is a clear divide in the impact before and after summer-2022, the latter period showing much larger impacts.
• The ONS error in the processing of NI labour market data has now been corrected in the reweighting exercise resulting in larger impacts on the NI data than the other countries in the UK.
• For summer-2022 onwards, the employment rate has been revised upwards by an average of 1.3 percentage points (pps), ranging from 0.7pps to 2.0pps.  The largest impact was in the August to October 2023 quarter.
• For this later period, the economic inactivity rate has been exclusively revised downwards by an average of 1.2pps, ranging from 0.7pps to 1.9pps.  The largest impact was in the August to October 2023 quarter.
• The unemployment rate has been revised downward slightly over the reweighting period by an average of 0.2pps, ranging from 0.1pps to 0.3pps.  The largest impact was in the September to November 2022 quarter.

The effect of these changes in comparison to the other UK countries and regions will not be available until the next publication of the Labour Market Report on the 17th December.  This release will include the newly reweighted series up to the August to October 2024 quarter.

More detail on the scale of the NI revisions is provided in the accompanying paper and tables available at: LFS - Background Information.

The related ONS article is available at: https://www.ons.gov.uk/releases/impactofreweightingonlabourforcesurveykeyindicatorsdecember2024

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