Excess mortality and expected mortality

According to CBS’ definition, excess mortality occurs when the observed number of deaths over a particular period is higher than the number expected for that same period.
Expected mortality, had no coronavirus epidemic occurred, has been estimated based on the observed number of deaths over the years 2015-2019. First, mortality on a weekly basis is established for each of the preceding years. Subsequently, an average mortality figure is determined for each consecutive week and the six surrounding weeks. These weekly averages offer an approximation of the expected weekly mortality, as the trend growth of population ageing has not yet been taken into account. For this reason, the weekly mortality figures were rescaled to fit the expected annual mortality over the year. For 2020, this is 153,402 and for 2021 the number is 154,887. The number for 2020 is taken from the ‘Kernprognose 2019-2060’ and the number for 2021 from the ‘Bevolkingsprognose 2020-2070’ (excluding the assumption of excess deaths due to the coronavirus epidemic). The margins around expected mortality are estimates, based on the observed spread of weekly mortality over the same five years. This method has been applied retrospectively to the expected mortality from week 1 in 2020.