This report analyses the development of mortality assumptions to build mortality tables to better protect retirement income provision. Mortality assumptions are necessary to ensure the sustainability of lifetime incomes. It explores considerations and traditional approaches for developing mortality tables, as well as provides an international overview of longevity trends and drivers over the last several decades, including the impact of the COVID-19 pandemic. The report also details the standard mortality tables developed across OECD member countries and offers guidelines to assist regulators and supervisors in assessing whether the mortality assumptions and tables used in the context of retirement income provision are appropriate.