Before revision:  As many countries lack reliable estimates of age-specific infection fatality rates, we map them from a reference country onto countries of interest based on remaining life expectancy . This scaling accounts for cross-country differences in the age structure, the health status, and the health care system. We also introduce easy to apply formulas to quantify the bias that would be required in death counts and infection fatality rates in order to reproduce a certain estimate of infections. Across the 10 countries with most COVID-19 deaths as of April 17 , 2020, our estimates suggest that the total number of infected is approximately 4 times the number of  ]  confirmed cases.
After revision:  As many countries lack reliable estimates of age-specific infection fatality rates, we map them from a reference country onto countries of interest based on remaining life expectancy as a marker to account for differences in age structures, health conditions, and medical services. Across 10 countries with most COVID-19 deaths as of April 17 , 2020, our estimates suggest that the total number of infected is approximately 4 times the number of ] confirmed cases.