The Human Mortality Database (HMD) contains original calculations of mortality rates and life tables for national populations (countries or areas), as well as the input data used in the construction of these tables. The input data consist of death counts from vital statistics, plus census counts, birth counts and population estimates from various sources. The main objective of the Human Mortality Database (HMD) is to document the longevity revolution of the modern era and to facilitate research into its causes and consequences. As far as possible, we follow four guiding principles in the creation of this database: comparability, flexibility, accessibility, reproducibility.