Some notes on excess mortality
Excess deaths are deaths from all causes above a baseline. That baseline often represents an expected number of deaths.
Different institutions use different baselines:
- Office for National Statistics: Past 5-year average (2015 to 2019).
- Public Health England: statistical models using the past five years of data.
- EuroMOMO: statistical models of ‘normal’ summers and winters.
Excess death calculations differ through choices of periods and baselines.
Where can I find data on excess mortality?
There many institutions collating COVID-19 surveillance deaths. There is no single source for frequent all-cause mortality.
There are two teams of researchers collating weekly and monthly mortality figures.
- Human Mortality Database: researchers at the University of California and the Max Planck Institute.
- World Mortality Dataset: researchers Ariel Karlinsky and Dmitry Kobak. Currently, this dataset covers 94 countries.
Why do we need to look at excess mortality?
For public health agencies, COVID-19 surveillance deaths have specific definitions. Those definitions differ between countries, which makes for challenging comparisons. Definitions can also differ within countries too: with the USA and UK publishing aggregate statistics.
Timeliness matters more for surveillance numbers than completeness. It is useful to look at deaths from all causes, to circumvent labelling problems.
A major limitation is mortality statistics are not available for all countries. The UN Statistics Division estimates some countries have under half coverage of death registrations. Some places do not have sufficient death reporting systems to give accurate counts.