From the 20^th to the 21^st century: Europe and its population after the year 2000

There are two approaches to projecting population trends and two reasons for doing so [**]. In the short run, they are designed to meet practical needs : to forecast future requirements for schools, teachers, housing and welfare ; every investment decision implies a population projection. In the long run, projections are another sort of exercise : the focus is on probable future patterns, the importance of recent trends is exaggerated and current population structures are all-important. In the present chapter, Jean Bourgeois-Pichat [***] proposes a third way of looking into the future : the very long term, where imagination reigns – and indeed, why not ? Anyone who had forecast a hundred years ago the extraordinary demographic changes we are experiencing now, would more appropriately have used imagination rather than extrapolation of the trends at that time.