The impact of COVID-19 on the individual lifespan can be measured by the difference in period life expectancy at birth (PLEB), an intuitive indicator of mortality conditions during a reference period. When mortality conditions are changing rapidly, however, that intuitive interpretation of the PLEB for short reference periods and of its change conflict with the assumptions under which the PLEB is derived.
To avoid assumptions about future mortality, I propose measuring instead the Mean Unfulfilled Lifespan (MUL), defined as the average difference between the actual and otherwise expected ages at death in a recent death cohort. For fine-grained tracking of the pandemic, I also provide an empirical shortcut to MUL estimation for small areas or short periods.
I estimate quarterly MUL values for the first half of 2020 in 142 national populations and 91 sub-national populations in Italy, Spain and the US. Across countries, the highest quarterly values were reached in the second quarter in Peru (3.90 years) and in Ecuador (4.59 years). Higher quarterly values still were found in New York and New Jersey, where individuals died respectively 5.41 and 5.56 years younger on average than their expected age at death.
Using a seven-day rolling window, I estimate the MUL peaked at 7.32 years in Lombardy, 8.96 years in Madrid, and 8.93 years in New York, but reached 12.86 years for the entire month of April in Guayas (Ecuador). These results illustrate how the MUL provides an intuitive metric to track the pandemic without requiring assumptions about future mortality.