We are transparent in showing revisions to UK gross domestic product (GDP) estimates; we publish real-time estimates of GDP and revisions triangles that show whether there is a bias in early estimates of GDP, while also providing commentary on the revisions performance of UK GDP.
Average quarterly GDP revisions from Quarter 1 (Jan to Mar) 1997 to Quarter 2 (Apr to June) 2023 in Blue Book 2023 were smaller than in the last two Blue Books; however, revisions were larger throughout 2020 and 2021, reflecting the higher levels of data uncertainty because of the coronavirus (COVID-19) pandemic.
Revisions to 2020 and 2021 annual GDP were larger than normal; however, this is not the case if you consider the size of the movements in GDP over this period, where the relative revisions over 2020 and 2021 are much more comparable with those prior to the pandemic.
One of the main explanations for revision to initial estimates of GDP in the pandemic was the introduction of intermediate consumption estimates that capture the inputs that are used as part of the production process.
This article focuses on GDP revisions over 2020 and 2021 and how they compare with those in the pre-pandemic period; we will continue to review the revisions performance of 2022 and beyond in future articles as data vintages mature.
There is a trade-off between the timeliness and accuracy of estimates of gross domestic product (GDP). As additional information becomes available, we have a more complete picture of economic activity in that period. This production cycle can take up to three years and naturally leads to revisions in our estimates of GDP. The annual Blue Book process is also when major methodological improvements are introduced in a consistent and co-ordinated way.
To assess revision performance of our GDP estimates, we can estimate:
the mean revision (MR), which shows whether there is a systematic tendency for initial estimates to be revised upwards or downwards
the mean absolute revision (MAR), which measures the absolute size of revisions so that upward revisions are not offset by downward revisions of the same magnitude
the mean square revision (MSR), which incorporates the degree of bias and the variance of the revision, as large revisions are treated more seriously than small revisions
This article analyses the revisions to our quarterly GDP estimates that were published in our UK National Accounts, The Blue Book: 2023 publication.Back to table of contents
Figure 1 shows the revisions to volume estimates of the quarterly change in gross domestic product (GDP) as part of implementing our annual national accounts, or "Blue Book". In Blue Book 2023, there was a mean revision (MR) of 0.03 percentage points to our estimates of the quarterly change in GDP over the period Quarter 1 (Jan to Mar) 1997 to Quarter 2 (Apr to June) 2023, and a mean absolute revision (MAR) of 0.09 percentage points.
Figure 1 would typically be an appropriate proxy of the impact of the revisions in a Blue Book, if there was a similar revision to the change in GDP for all periods. However, this was not the case in Blue Book 2023, as revisions were higher during the coronavirus (COVID-19) pandemic of 2020 and 2021. This reflected the expected higher levels of data uncertainty. For example, the MR over the period Quarter 1 2020 to Quarter 4 (Oct to Dec) 2021 was 0.21 percentage points, while the MAR was 0.24 percentage points.
We publish monthly snapshots of quarterly GDP, allowing comparison between a first estimate of quarterly GDP with one that is published months later. Our focus is on those estimates published 3, 24 and 36 months after the first estimate of quarterly GDP, reflecting the three-year production cycle of UK GDP.
Table 1 shows that there is a zero mean revision (MR) at t plus three months over the period Quarter 1 1961 to Quarter 4 2020, implying that there is no tendency for the first estimate to be revised up or down. That said, the revisions performance has not been constant over time, where revisions have tended to be larger in earlier periods and around turning points in the economy, where uncertainty is likely to be more pronounced.
Table 1 shows that the MR is a little higher when comparing the first published quarterly estimate with the estimate published three years later. This analysis continues to show that while initial revisions (t plus three months) are not statistically significant, the revisions that reflect the supply and use tables (SUTs) balancing process (t plus 36 months) are now marginally statistically significant over the full timespan.
|T + 3||T + 36|
|T Score |
|T Score |
|1961 Q2 |
|1961 Q2 |
|1970 Q1 |
|1980 Q1 |
|1990 Q1 |
|2000 Q1 |
|2010 Q1 |
Download this table Table 1: There is some evidence that revisions are marginally statistically significant when looking at the final quarterly estimate of GDP.xls .csv
Figure 2 shows that the quality of early quarterly estimates has improved significantly over time. There have been improvements to the measurement of GDP as well as a lower degree of volatility in the UK economy, although the pandemic has proven to be an exception. Figure 2 shows that the MAR is larger at the three-year horizon for each of the last six decades. As additional information becomes available, the revision increases between t plus three months and t plus 36 months. However, the MAR is less in recent periods, including a reduction between these MAR revisions as later data are incorporated. It is likely that these revisions reflect the impact of balancing our full range of information in a SUT framework for the first time, and methodological improvements, which cannot be anticipated at the time of the first estimate.
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Revisions are a natural part of statistical compilation and there is a balance between timeliness and accuracy, making the best use of the data available at the time. The Office for National Statistics (ONS) continue to publish full revisions performance information for gross domestic product (GDP) and its components in a timely and transparent manner.
The substantial impacts of the coronavirus (COVID-19) pandemic during 2020 and 2021 highlighted challenges in the measurement of intermediate consumption for sectors of the economy.
We believe that we could improve the overall revisions performance of our early estimates of GDP if we could bring in timely information on intermediate consumption. We are currently investigating how this can happen. We are also reviewing if we can improve how we communicate uncertainty in early estimates of GDP and will publish further information on this in due course.Back to table of contents
Gross domestic product (GDP)
A measure of the economic activity produced by a country. The three approaches used to measure GDP are the:
A more detailed glossary is available.Back to table of contents
More information about strengths and limitations of national accounts data used in the Blue Book can be found in our Gross domestic product (GDP) Quality and Methodology Information (QMI).Back to table of contents
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