In dealing with significant fiscal challenges posed by ageing and the climate transition and the risk of rising future debt burdens, countries can draw on the lessons from past episodes of large and sustained reductions in debt-to-GDP. Work in the November 2023 OECD Economic Outlook found that there have been 34 sustained debt reduction episodes in OECD countries since the late 1970s, with 25 countries having experienced at least one such episode during this time. Reductions in the debt-to-GDP ratio have mainly hinged on achieving and sustaining a primary surplus over several years, largely via expenditure restraint, as well as favourable cyclical conditions and low interest rates. Expenditure restraint has often been accompanied by growth-friendly shifts in the composition of public spending. […]