An error has been identified in the Retail Prices Index (RPI) in 2020 caused by an issue with the 2018 to 2019 Living Costs and Food Survey (LCF) dataset, which is used to produce the weights underpinning the RPI.
There is no impact on the Consumer Prices Index including owner occupiers’ housing costs (CPIH) or the Consumer Prices Index (CPI), for which weights are calculated using more comprehensive national accounts data sources. These sources draw on a wider range of survey and administrative sources than just the LCF.
We are taking steps to safeguard against future RPI errors of this nature. The LCF will undergo an end-to-end review of the current quality assurance processes. The way LCF results are compiled and used in producing RPI weights will also be reviewed with a view to strengthening and improving the processes.
Following the outcome of the 2020 consultation on the RPI methodology, it is our intention to bring the methods and data sources of the CPIH into the RPI, which will reduce the RPI’s over-reliance on LCF weights data.
In line with the published revisions policy for consumer price inflation statistics, the RPI will not be revised. This error will be corrected in the February 2021 RPI, due to be published on Wednesday 24 March 2021 as part of the regular, annual update of RPI weights.
However, we have estimated that if the corrected LCF dataset had been used to calculate the 2020 RPI weights, it would have led to an upward revision of 0.1 percentage points to the published RPI annual growth rate in six months of 2020.
| Published RPI All-items 12-month rate | Corrected¹ 12-month rate | Revision in percentage points | |
|---|---|---|---|
| Feb-20 | 2.5 | 2.5 | 0.0 |
| Mar-20 | 2.6 | 2.7 | 0.1 |
| Apr-20 | 1.5 | 1.5 | 0.0 |
| May-20 | 1.0 | 1.1 | 0.1 |
| Jun-20 | 1.1 | 1.1 | 0.0 |
| Jul-20 | 1.6 | 1.7 | 0.1 |
| Aug-20 | 0.5 | 0.6 | 0.1 |
| Sep-20 | 1.1 | 1.2 | 0.1 |
| Oct-20 | 1.3 | 1.4 | 0.1 |
| Nov-20 | 0.9 | 0.9 | 0.0 |
| Dec-20 | 1.2 | 1.2 | 0.0 |
| Jan-21 | 1.4 | 1.4 | 0.0 |
Download this table Table 1: RPI published and corrected¹ 12-month rates with revision (in percentage points)
.xls .csvUsing the corrected LCF data would also have led to an upward move to the RPI All-items index level in the majority of months of 2020.
| Published RPI All-items Index (UK, January 1987 = 100) | Corrected¹ RPI All-items Index (UK, January 1987 = 100) | Revision in percentage points | |
|---|---|---|---|
| Feb-20 | 292.0 | 292.0 | 0.0 |
| Mar-20 | 292.6 | 292.7 | 0.1 |
| Apr-20 | 292.6 | 292.6 | 0.0 |
| May-20 | 292.2 | 292.3 | 0.1 |
| Jun-20 | 292.7 | 292.8 | 0.1 |
| Jul-20 | 294.2 | 294.3 | 0.1 |
| Aug-20 | 293.3 | 293.4 | 0.1 |
| Sep-20 | 294.3 | 294.4 | 0.1 |
| Oct-20 | 294.3 | 294.5 | 0.2 |
| Nov-20 | 293.5 | 293.7 | 0.2 |
| Dec-20 | 295.4 | 295.5 | 0.1 |
| Jan-21 | 294.6 | 294.8 | 0.2 |
Download this table Table 2: RPI published and corrected¹ index values with revision (in percentage points)
.xls .csvWe are aware RPI is used in certain financial contracts and so we are publishing this notice outside of trading hours.
Contacts:
Telephone: Consumer price inflation enquiries: +44 (0)1633 456900
Email: cpi@ons.gov.uk