Excess deaths are those deaths that occur above a region’s past baseline. Data scientists calculate the metric by determining the average deaths for a country or region over a period of several years—then comparing this past average to the deaths that occured in the current year.
The deaths occurring in the current year above that past average are the excess deaths. In New York City during the spring 2020 surge, for example, about four times more people were dying each week compared to the same time period in previous years.
During the pandemic, excess deaths have become a useful way for scientists to estimate the true toll of COVID-19. Especially during the earlier months of 2020, limited access to testing meant that many people who became infected with the coronavirus were not able to get the positive test required for their illness (or death) to actually be counted as a case. (In the U.S., this recording gap is currently causing issues for families who lost loved ones to COVID-19 early in the pandemic and are now seeking federal aid.)
Plus, the pandemic caused hospital systems to shut down and inspired widespread hesitancy for anyone seeking medical care for a non-COVID reason. The death of someone who had a heart attack and couldn’t get a hospital bed because of COVID-19, for example, is not a COVID-19 death but was undoubtedly caused by the pandemic.
Excess deaths, as a metric, allow researchers to see how the pandemic has impacted a country or region—above the official COVID-19 death counts. And a recent audit from Peru provides new evidence for this metric’s value.
The country essentially audited its COVID-19 deaths data to address undercounting. Government officials checked thousands of death certificates from 2020, and added any COVID-related deaths to past totals—which previously only included those Peruvians who had positive PCR tests.
After the audit was complete, Peru’s COVID-19 death toll rose by almost three times—to 180,000 deaths. The country now has the highest official death rate in the world: one in every 177 people.
When plotted over time, Peru’s revised death data match closely with its excess deaths, as calculated by the Financial Times data team. This audit—and its match with excess deaths—shows that excess deaths do, in fact, show the true toll of COVID-19 in a country.
It’s also notable as the first time a country has done such an audit on a wide scale. Some states (such as Washington) have added COVID-19 deaths to their official counts periodically, as they process death certificate backlogs, but none have done anything on Peru’s level.
Future death certificate audits and excess death analyses may help us understand the true toll COVID-19 has taken on the U.S. and the world.