Measuring Mortality Using Public Data Sources 2019-2023 (October 2019 - June 2023)

Observed Death Notices

Each death notice pertaining to a date of death between 01 October 2019 and 02 July 2023 (the period under investigation) was read, cleaned and classified. Cleaning involves first classifying deaths as within Ireland or abroad and then removing:

• Death notices pertaining to expatriate deaths
• Death notices pertaining to Northern Irish citizens
• Nulls – these are empty records which contain no information, a result of the web-scraping process
• Duplicates, which are so rare as to be negligible

Classification Process

For the first three releases in this series, classification of location of death was undertaken by a team who read every individual notice and manually classified the death notice as referring to a death in Republic of Ireland, Northern Ireland or elsewhere abroad. For this and the previous release a new method of classification was developed by a CSO statistician using a machine learning classification model. The models were trained on the results of the manual classification work done during the previous releases. These models when applied to any newly scraped data provide an appropriate classification for each new death notice. For consistency the classification model has been applied to all RIP data contained in this release. The result of this change means that some historical figures will have been updated. Furthermore, there is no limit on when a notice can be uploaded to RIP and as such new notices may have been added recently that relate to deaths that occurred months or very occasionally, years ago. In all cases a date of death is specified and additional notices are only included if they relate to the reference period of this release.

Expected Death Notices

Expected death notices are calculated as the death notices we would have expected to see during the period of interest in the absence of the pandemic. The initial releases calculated expected death notices in two different ways:

• The average of the last two years
• The average of the last three years

For the previous release we moved to a single average over the four years prior to the pandemic (2016 - 2019). The reason for this change was to align the baseline average with the methodology used by Eurostat in calculating excess deaths. By aligning this release with the Eurostat methodology, it is possible to compare excess deaths with other European countries. 

Eurostat continue to produce a monthly report on excess deaths using the 2016 - 2019 baseline average. Due to the demographic nature of the Irish population, particularly a growing population over 65 years old and a general trend of an increasing number of deaths over the last 12 years, this baseline may be no longer be an appropriate indicator of expected deaths. For this reason, two alternative baselines have been presented.

• The average of the previous 4 years
• The average of the previous 4 years but excluding 2020 data.

This approach of excluding the first year of the pandemic mirrors a similar approach by other countries including the UK Office of National Statistics who use a 5-year average that excludes 2020 as a baseline figure for expected deaths.

Excess Mortality and the Choice of Period of Interest

To calculate excess mortality, we subtract the number of death notices we would have expected to see in the absence of the pandemic from the number of death notices we observed. 

For our period of interest in this release, we cover the months January 2020 to June 2023, which includes two peaks associated with COVID-19 and a further peak in December 2022 that appears to be associated with high levels of respiratory viruses circulating in the population. Further analysis of trend in excess deaths was also conducted back to 2000 to provide additional context.

Figure 2 below provides some context on excess deaths in the 10 years prior to the pandemic. Between January 2010 and December 2019, 82 out of 120 months (68%) had a positive figure for Excess Deaths. 

Comparison of Death Notices to Deaths by Occurrence

Deaths by Occurrence means the number of deaths is calculated based on the date on which they occurred. Death notices were also analysed by date of death as per the death notice. For the comparison of the two sources, we have looked at all registered deaths as of 02 July 2023. All GRO data after 2020 is provisional and was extracted at a single point in time (03 July 2023). 

While it is important to note the experimental nature of this analysis, death notices continue to closely track actual deaths by occurrence dates. This method would seem to provide a robust, timely and accurate estimation of mortality in Ireland.