In the paper other than economic and biological determinants of fertility behaviour are discussed. The qualitative dimensions in the shaping of fertility decisions are given importance. Described is the "wealth flow theory" of material and non-material goods, and the theory of the "optimal family", trying to maintain the balance between the "costs" of children and the "benefits" for the parents. In all modern societies wealth flows from parents to children, and material and non-material investments (time and energy) in children have grown to the extent that they destroy the balance between "costs" and "benefits" which results in the lowering of the "optimal" family size, and in turn influences the choice of low fertility strategies. The discussion opens new perspectives in the study of factors influencing fertility decline, and points to the causes of inefficiency of population policy measures practised in European societies. The population "optimum" is often defined in accordance with the existing situation, and the distribution of political power. Population policy measures are implemented in the context of other policies such as, family, economic, financial, health, social and educational policies even though their goals are not necessarily the same. Another reason for the inefficiency of population policies is the fact that these policies represent collectivistic against individual and family interests. Experience shows that changes in fertility patterns are influenced by overall social changes more than by population measures.