This paper aims, first, at assessing the relative importance of working age population and participation rates to explain labour force developments in the euro area between 1983 and 2000. It also compares participation rates in the euro area vis-à-vis the US, considering age and gender groups. It shows that the effect of population growth on labour force developments is losing importance relative to the effects of changes in the participation rate. Indeed, in the last few years, the effects of changes in the participation rate have exceeded those of the increase in working age population. This trend is expected to continue in the coming years. As regards the comparison of the euro area with the US, it shows a continuing large difference in women’s participation rate and among the youngest and oldest men’s age groups in the US versus the euro area, giving room for future positive contributions coming from participation in the euro area.