"In this contribution the concept of population policy theory is defined. Also, the relevance of studying these theories in order to assess the demographic impact of population policy is discussed. The policy theory underlying the pronatalist marriage and family founding loans is evaluated as is the policy theory underlying antinatalist family planning communication programs. It is concluded that the behavioral mechanisms behind the two policy measures appear not to work in a way the policy theory assumes they work, i.e. appear not to be able to change fertility behavior substantially." The geographic focus is worldwide. (summary in FRE, ITA)