This paper forms part of on-going OECD work on the economic assessment of public pension systems in view of the process of the ageing of populations. It provides indicative estimates of the likely size of public pension liabilities in the main seven economies based on simplifying assumptions, and analyses various methods of financing these liabilities. The methodology developed here is based on the so-called generational accounts approach. Such accounts indicate in present-value terms the lifetime financial burden government programmes impose on present and future generations. Up to now, the methodology has been used to estimate public pension liabilities in France and Belgium, in the framework of the 1993 OECD Economic Surveys for those countries ...