National Statistical

Each week the ONS publishes death registration data which include estimates of excess deaths, the difference between how many people have died and what we would expect. By estimating excess deaths in England and Wales, Scotland, Northern Ireland, and the UK, we can identify health threats impacting mortality. We are always working to improve our statistics to ensure they provide the most value and we have been developing our approach to how we estimate excess deaths. Here Dr. Vahé Nafilyan outlines our plans for future improvements in this important area.

Excess deaths refer to the number of deaths that occur above (or below) what we would expect under normal circumstances. We compare the actual number of deaths in a certain period with the number we would expect based on historical data. During the COVID-19 pandemic, excess deaths estimates were particularly important. They helped us understand the impact of the pandemic on mortality by capturing deaths directly and indirectly related to the virus. This was vital for informing public health responses. Beyond the pandemic, excess deaths estimates continue to be valuable for identifying emerging health threats and monitoring the overall health of the population, such as during bad flu seasons. 

First steps  

As outlined in our previous blog, in February 2024 we launched our current method for estimating excess deaths following collaborative work with partners from across government, the devolved administrations and the actuarial profession. This approach takes into account how the population has grown and aged over time and excludes weeks and months that were significantly impacted by COVID-19 deaths when estimating the number of expected deaths. This allowed us to more accurately reflect changes in the demographic composition of the population and mortality trends over time. As well as being closely aligned with the approach used by the Office for Health Improvement and Disparities (OHID), the methodology was implemented across all four countries of the UK, making it possible to form a wider picture of excess deaths.   

Further improvements  

The estimates produced by the current method have been classified as Official Statistics in Development, reflecting the ongoing need to improve our statistical models and refine the methodology.  

Going forward, we are working towards obtaining Accredited Official Statistics status for our excess deaths estimates, which will mean they meet the standards outlined in the Code of Practice for Statistics. In November 2024, we presented a paper at the UK Statistics Authority’s Methodological Assurance Review Panel (MARP) outlining a range of options for how we might further refine our approach. Based on feedback from the MARP, we are proposing to make a few improvements. 

Accounting for public holidays 

Most of our mortality statistics are based on when deaths are registered rather than when they actually occur. This means that mortality rates in a given week or month are influenced by the number of working days during the period. Although our current statistical models account for the number of weekdays in a period, they do not factor in that there may be bank holidays during that time, when registration offices are closed and any deaths have to be registered at a later date.  

We are exploring various approaches to account for the effect of public holidays, leading to more reliable estimates of expected and excess deaths in the periods of time that are affected, such as Christmas and Easter. 

Refining the age groups 

Our current statistical approach allows for different mortality trends and seasonal patterns by broad age group when estimating the number of expected deaths. However, we are exploring whether we can use a more detailed age breakdown, allowing us to better account for age-specific variations in mortality time series. This will improve the estimation of expected deaths, and therefore the estimation of excess deaths. This approach would also be more closely aligned with the methodology used by OHID. 

Better reflecting uncertainty  

Unlike counts of registered deaths, excess deaths are estimated using statistical techniques, meaning there is no single “true” measure of excess deaths. The current approach allows confidence intervals to be produced around our estimates of expected and excess deaths, reflecting the fact that they do not refer to an actual observed value. We are currently exploring ways to account more fully for all sources of uncertainty in the estimates. By better accounting for uncertainty, users can more easily understand the degree of confidence in the estimate, while also reducing the risk of misinterpretation and importantly, misreporting in this complex topic.   

More detailed breakdowns of excess deaths 

In our Deaths registered weekly in England and Wales publication, we report excess deaths both for the UK as a whole and separately for each of the four nations, further divided by age group and sex for the UK and England and Wales. Scotland and Northern Ireland publish their own excess death statistics too. 

To provide more granular insights of trends in excess deaths, we are aiming to incorporate monthly estimates broken down by sub-national geographies (for example, local authorities in England and Wales), area deprivation groups and broad cause of death, which are currently produced by OHID. This deeper insight will help policy makers identify areas of emerging need among different communities, allowing them to better tackle health challenges facing the population.   

We welcome your feedback 

If you are interested in further detail on our proposals, please refer to our MARP paper. The paper also includes options that we are not proposing to take forwards for further development based on feedback from the Panel, such as increasing the length of the baseline period from which the number of expected deaths is estimated (currently five years). 

We are committed to putting users’ needs at the centre of our ongoing development work for these vital mortality statistics, and we welcome feedback on our proposals before we make any amendments to our approach throughout 2025. To share your views, please contact us at health.data@ons.gov.uk quoting “excess mortality” in the subject line.