Excess mortality is an epidemiological concept typically defined as the difference between the observed number of deaths in a specified time period and the expected numbers of deaths in that same time period. Estimates of excess deaths can provide information about the burden of mortality potentially related to the COVID-19 pandemic, including deaths that are directly or indirectly attributed to COVID-19.
Throughout this report, counts of deaths for 2020 and 2021 are compared to an average number of deaths recorded over the previous 5 years (2015-2019). These average or baseline counts serve as a proxy for the expected number of deaths, so comparisons against baseline counts can provide an indication of excess mortality. The minimum and maximum counts from 2015-19 are also included to provide an indication of the range of previous counts. Minimums and maximums for any given week can be from any of the five years from 2015-19. As mortality during 2020 had periods where deaths were significantly lower than expected, 2020 has not been included in the baseline average.