Population ageing is one of the megatrends shaping the future of societies and labour markets. The old-age dependency ratio - the ratio of individuals aged 65 and older to the working-age population - is projected to reach unprecedented high levels in many OECD countries in the next 35 years. This edition of the OECD Employment Outlook discusses the enormous challenges this megatrend poses to current living standards, and social cohesion more generally. The consequences of an ageing workforce for productivity growth are also analysed. The main message of this edition is that without swift changes in policies and behaviours, GDP per capita growth will slow down significantly in most OECD countries. Mobilising untapped labour resources, including older workers but also women in many countries, will be key to offsetting this trend. This Outlook examines policies to address these demographic changes, with a focus on increasing employment of older workers while ensuring that they can thrive in the labour market. It shows that a successful strategy must be built around incentives, employability and opportunities. Policies to preserve and develop worker skills and job mobility will also be essential to maintaining productivity growth.