Demographic changes do not affect just the volume of the working population. They also affect its age structure. It is widely held that the ageing of the entire population should go hand in hand with labour force ageing. The reality is more complicated. The two ageing processes are staggered and they neither last for the same length of time nor are of the same magnitude. It is only after 2006 that baby boomer ageing will trigger a long phase of growth in the proportion of over-60s. However, this ageing has been tending to push up the average age of workers for several years now and this process will slow substantially after 2006. A marked resumption of this ageing would only be seen if the retirement age were to be raised. Do these changes in the age structure have any significant repercussions? Their effect on productivity, training incentives and the average unit labour cost are not necessarily negative, especially as regards the effect on average productivity. Nevertheless, the ageing of the labour force calls for training to be stepped up. Moreover, seniority-based remuneration systems may prompt upward pressure on unit production costs. Even if this effect were to remain moderate overall, it would form an obstacle to the potential increase in participation rates among older citizens. Last but not least, demographic ageing could have more significant effects in the professions and sectors experiencing greater demographic changes than the average national trend.