He reaches the conclusion that immigration is necessary for Germany for reasons of a socio-demographic nature, but also that it is difficult to specify the volume required, the timing or the other desired characteristics. In his opinion, it is the elimination of determinants at the root of the refugee phenomenon which would allow the easiest method of regulating international migratory flows. Sustainable solutions would be those which would ease the distressful situations of the refugees, but would, first and foremost, be preventative action aimed at avoid or, at the very least, limiting, the large-scale outflows which occur at present. Although scorned at a certain point in time, the influence of mortality has been underestimated for the most spectacular progress in that field has led to a decline in infant mortlaity which, in turn, results in a brake on the fertility decline. In recent years, the increase in life expectancy has almost entirely been due to the campaign against old-age mortality.
Fertility is the greatest determinant for age structure.
The age structure of immigrants can only help slightly in attenuating this trend towards ageing. Finally, the author describes the forthcoming ageing of the populations in the developing countries and the difficult adaptation processes which it will engender.