FOI reference: FOI-2024-1822
You asked
You have recently changed the criteria for collation, composition and publishing of excess deaths in the UK.
Bearing in mind the importance of your figures published weekly by the government and medical establishment during the height of the COVID-19 restrictions to reinforce behaviour, the longevity and historical use of your old formula and the large increase in excess deaths in recent years, my questions are:
1. What prompted this change?
2. Who authorised it?
3. When was this change first proposed?
4. Why have you removed reference to Pandemic deaths in 2020?
5. Have you applied your new formula retrospectively to all deaths 2019 - 2023 and if so, what is the result and how did it compare to the figures published by you in 2020 and 2021?
We said
Thank you for your request.
1. Our previous methodology did not take account of the growth and ageing of the UK population (all else being equal, more people means more deaths, particularly if a greater share of the population are elderly); nor did it reflect recent trends in population mortality rates, which were generally falling until 2011 before levelling off until the onset of the pandemic. Accelerating population growth, particularly among people aged 70 years or older, during the COVID-19 pandemic (see Figure 3 in our article) provided an impetus to instigate this methodological development work.
2. The new methodology was not authorised by a specific individual. This decision was based solely on statistical and methodological considerations, led by ONS in its capacity as the UK's independent national statistical institute.
The approach was developed by a cross-organisation working group with representatives from different areas of the Office for National Statistics, the Office for Health Improvement and Disparities, the UK Health Security Agency, Public Health Wales, the Welsh Government, National Records of Scotland, the Northern Ireland Statistics and Research Agency, and members of the actuarial profession.
During its development, the work was reviewed by the UK Statistics Authority's Methodological Assurance Review Panel and the UK Statistics Authority Board.
3. The formation of the cross-organisation working group mentioned above was announced in February 2023. The aim of the group was to review current (at the time) methods and explore a broad range of alternative approaches, finally resulting in the changes we implemented in February 2024.
4. The pandemic saw a large increase in death registrations, particularly in certain weeks and months that coincided with "waves" of infection (for example, when new COVID-19 variants became widespread in the population). To avoid these periods affecting estimates of expected deaths in subsequent periods, they are removed from the dataset used to estimate the number of expected deaths so that they do not contribute to the mortality baseline. This means that estimates of excess deaths in subsequent periods relate to the additional deaths registered in the period, over and above what would be expected from previous periods had they not been extraordinarily affected by the pandemic.
It was always the case with our previous approach that data for 2020 were removed when calculating the five-year average number of deaths. The expected number of deaths in 2021 was estimated as the average of deaths registered from 2015 to 2019 rather than 2016 to 2020, to avoid the pandemic distorting the excess deaths calculation. The expected number of deaths in 2022 was estimated as the average of deaths registered in 2016, 2017, 2018, 2019 and 2021.
In contrast, individual weeks and months, rather than whole years, that were substantially affected by the immediate mortality impact of the pandemic are removed from the expected deaths calculation under the new methodology. These are weeks and months where COVID-19 was given as the underlying cause of death for at least 15% of all deaths registered in the period across the UK: April and May 2020, and November 2020 to February 2021 for monthly data; and Weeks 14 to 22 of 2020, and Week 45 of 2020 to Week 8 of 2021 for weekly data.
5. We have estimated excess deaths using our new method, and compared with estimates from our previous approach, from 2011 to 2023. Full results can be found in our methodology article. Annual estimates for 2019 to 2023 are provided in the associated download.