ANTONIO GOLINI AND ROBERTA VIVIO
Population ageing, for its numerical importance, its proportional weight, the speed of its growth, its geographical differentiation, and its multidimensional aspects will, demographically speaking, characterize this last part of the twentieth century and the beginning of the twenty-first in Western countries. However, starting from the early decades of the next century it will also increasingly characterize many of the countries which are currently classified as 'developing', so that while the twentieth century will be remembered as the century of great and rapid population growth, the twenty-first will be remembered as the century of population ageing.
This great demographic change will come to full fruition with the passage of only two or three generations, i.e. in an extremely short period of time both from a demographic point of view and from a social and cultural one. The speed of the phenomenon is therefore the first great difficulty which societies will have to face. The second can be found in the intensity of the phenomenon, since in some populations, the percentage of over-60s could exceed 40-5 per cent of the total population and that of the over-80s, 10-11 per cent. The third is the duration of the population ageing process with which Western societies must continue to live for a long time to come. Even if this demographic transition were to come to an end within the next few decades, as is possible and perhaps desirable, and if we could therefore reach the target of more or less zero population growth, the population ageing process would come to an end well after zero growth was achieved. What is more, even assuming that stationarity is achieved, the growth in population ageing would only cease from a quantitative point of view, but not from a qualitative one, since further expected gains in the fight against disease and further expected improvements in life expectancy would contribute to a significant change in the health conditions of the population and more generally in the epidemiological____________________