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At the beginning of March, Andrew Noymer felt a familiar twinge of doubt. He was watching countries across Europe and North America begin to record their first deaths from COVID-19, and he knew there could be problems with the data. Even in a normal winter, some deaths caused by influenza get misclassified as pneumonia. If that can happen with a well-known disease, there were bound to be deaths from COVID-19 going unreported, thought Noymer, a demographer at the University of California, Irvine. “I just remember thinking, ‘this is going to be really difficult to explain to people’,” he recalls.