The reason for insufficient offspring is a decline in the birth rate. Quantitative demographic determinants can be explained by ideal characteristic values of population as well as structural properties of society. The low fertility as an influential parameter causes not only a decline in population but also age-structural changes in the composition of population, which come along with extensive social consequences. As consequences will retroact especially on young generations and therefore increasing the reasons for a low birth rate, the demographic trend unfolds its own momentum. However, measures to secure sufficient offspring encounter unfavourable conditions for action. Monetary and material incentives of fertility are of different demographic effectiveness and have lost importance. Instead of pursuing a passive arrangement of the consequences of demographic change by unprogressively treating the symptoms, society and state have to focus on fighting the causes of the decline in the birth rate actively. It turns out that the largest potential for actions can be developed at the national level.