Is ageing a threat to our societies' prosperity? How should resources be shared between the working generation and its dependent older citizens? How should pension, health and long-term care best be reformed? How can older people's contribution to society and economic prosperity be enhanced? Within the next decade, the numbers of retired people in OECD countries will start to grow much faster than those of working age. In the absence of major changes to pension systems and to the way people allocate their time between education, work and leisure, it is likely that fiscal and social strains will start to emerge. Some groups may be unfairly burdened through high taxation and others would face unexpected reductions in their material living standards. The appropriate policy response is multi-faceted, covering fiscal, social, labour market, financial market, health and education policies. An important part of the strategy for maintaining prosperity in an ageing society will involve encouraging people to work longer by making it financially more attractive for them to do so. In turn, this could entail reforms to traditional public pension systems and other social policies, as well as fostering the development of alternatives to public systems that give individuals more flexibility in deciding when to retire. Consequently, financial market infrastructures will need to be strengthened to cope with large increases in private pension fund assets. Through this multi-disciplinary study, the OECD points to the need to take action now by implementing a comprehensive and consistent set of policies.