When the Institute for Health Metrics and Evaluation at the University of Washington released its estimate that COVID-19 had killed 912,345 people in the U.S. by May 6, 2021, many were shocked. That’s 60% higher than the 578,555 coronavirus-related deaths officially reported to the U.S. Centers for Disease Control and Prevention over this same period. How can two estimates differ so widely? It’s not like the Institute for Health Metrics and Evaluation researchers stumbled upon a morgue of more than 300,000 dead people who hadn’t been tracked elsewhere. Here’s what goes into some of the various counts of COVID-19 pandemic deaths and how I as a statistician think about their differences.