Death, Demography and the Denominator: Age-Adjusted Influenza-18 Mortality in Ireland

Using the Irish experience of the Spanish flu, we demonstrate that pandemic mortality statistics are sensitive to the demographic composition of a country. We build a population database for Ireland’s 32 counties with vital statistics on births, ageing, migration and deaths. We show how age-at-death statistics in 1918 and 1919 should be used to construct the age-adjusted mortality statistics necessary to make comparisons across time and space. We conclude that studies of the economic consequences of Influenza-18 and Covid-19 must better control for demographic factors if they are to yield useful policy-relevant results. For example, while Northern Ireland has a higher crude death rate in the current pandemic, it also has an older population; age-adjusted mortality paints a very different picture.