Ageing is an inevitable, albeit a slow process, as are all population movements. Moreover, it takes several
decades for all its effects to work out : it is in every sense a time bomb.
At first, it appears harmless ; it may even seem beneficial, for it reduces the relative number of children who are
supported by the working population. It is only 30 or so years after the drop in the fertility rate that it begins to produce
deleterious effects, with a growth in the numbers of «young-elderly» who cost, on average, two to three times
more to society than children. 15 to 20 years later on comes an explosion of the health costs of the «elderly-elderly
». The full economic and social consequences then combine, producing a major crisis.
In the developing countries, ageing is just beginning and will only become an acute problem in the second half of
the century, a date too remote for to-day’s political leaders.
In the rich countries the first consequences began to appear at the start of the XXIst century, but the process will
accelerate from 2020 onwards. What makes the analysis of the problem and any forecasts complicated, is that the
growth of the population was not linear during the XXth century. This growth was characterised by a succession
of baby-booms and baby-busts, the former delaying the impact of ageing and the latter accelerating it.
Ageing poses new and major challenges to society and requires a dramatic change of mentalities and policies to
address them.
The article, amply illustrated, covers the whole world and stresses the global nature of the phenomenon, which
can only marginally be alleviated by migrations from developing to developed countries.