Why official covid-19 deaths do not capture the pandemic’s true toll
A lack of testing is the main reason, but there is a better way to gauge the real cost
KEEPING TABS on covid-19’s toll can feel like trying to count grains of sand on a beach. According to governments’ official counts, almost 4.7m people diagnosed with the disease have died. Yet the real figure is much higher. The Economist’s excess-deaths model puts it between 9.6m and 18.2m people, with 15.6m our single best guess, as of September 21st. Calculating the cost of the pandemic matters. It influences how governments and health-care systems respond, and how aid and vaccines are distributed. Why, then, are official statistics so wrong?
Recording a case of SARS-CoV-2 almost always involves administering a covid-19 test. But countries’ capacity to identify and report infections is limited. The Economist estimated in September last year that probably just one in 20 people infected globally thus far had entered official statistics. At the time, that implied about 600m uncounted infections. The problem is worst in poor countries, making comparisons with rich places largely meaningless. Take the Democratic Republic of Congo as an example. According to its official statistics, there have been only 56,000 cases and 1,000 deaths in a country of 92m people. But other evidence points to that being a huge undercount. About 5% of Congo’s members of parliament have died with covid-19, for example. That is 4,500 times the official rate in the country’s general population.
Testing is not the only hurdle. Some people who tested positive for covid-19 died from other causes, and were thus not strictly victims of the pandemic. (That said, such cases are probably rare: research suggests that people dying with covid-19 would on average have survived another decade, were it not for contracting the disease.) You do not have to catch covid-19 to be a victim. Other preventable deaths occurred because of the pandemic, for instance through overburdened hospitals or more reckless driving on emptier roads. And, counterintuitively, the pandemic may have saved lives too, as people shielding themselves avoided the flu and other diseases. Even if everyone who died directly from covid-19 were accurately counted, it would not represent the true toll.
Fortunately there is a better way to gauge the pandemic’s true death toll. “Excess mortality” is the gap between the actual number of deaths that occur and the amount that would have been expected under normal circumstances. It relies on the assumption that any unexpected deaths were caused by the pandemic and, as death counts tend to change little from year to year, that appears reasonable. In rich countries that test extensively for covid-19, the number of deaths attributed to the disease tends to be close to the number of excess deaths, which suggests that difference in testing, rather than indirect deaths, is by far the largest source of bias.
We are publishing an estimate of the pandemic’s real human cost around the world that is updated daily, using a machine-learning model to fill in the gaps where excess deaths are not reported. The model is not perfect: estimating excess deaths for every country since the beginning of 2020 is a complex task. (A deep-dive into our model’s methodology and the underlying data and code are available on GitHub.) But it is a better measure than official counts. Allocating aid according to official metrics would be a grave mistake, for instance, because the countries least able to test their dead would appear falsely to have suffered less. An estimation of excess deaths makes comparisons between countries with different testing and reporting capacities possible. That could lead to better decisions about how to help the places most in need.