Advanced and developing economies are experiencing a swift process of population ageing that will shape both long-run macroeconomic trends, such as economic growth, as well as short-term business cycle fluctuations. Although the implications of population ageing on countries’ fiscal capacity have been extensively analysed, this column argues that secular shifts in demographics can also influence the effectiveness of fiscal policy as a demand-management tool. Using a New Keynesian model with a lifecycle structure,  it shows that output fiscal multipliers are larger in younger economies.