If Catholics are forbidden to use contraceptives, then why are population numbers in Catholic countries declining?
Answer: Firstly, here is the official position of the Church regarding the question of birth control. The “Compendium of the Social Doctrine of the Church” (Rome, 2006) deals with this question under the title: The Family is the Sanctuary of Life (Nos. 230-237). (See: (http://www.vatican.va/roman_curia/pontifical_councils/justpeace/documents/rc_pc_justpeace_doc_20060526_compendio-dott-soc_en.html#I. THE FAMILY, THE FIRST NATURAL SOCIETY)
232. The family contributes to the social good in an eminent fashion through responsible motherhood and fatherhood, the spouses’ special participation in God’s work of creation. The weight of this responsibility must not be used as a justification for being selfishly closed but must guide the decisions of the spouses in a generous acceptance of life. In relation to physical, economic, psychological and social conditions, responsible parenthood is exercised both in the duly pondered and generous decision to have a large family, and in the decision, made for serious reasons and in respect of the moral law, to avoid for a time or even indeterminately a new birth. The motivations that should guide the couple in exercising responsible motherhood and fatherhood originate in the full recognition of their duties towards God, towards themselves, towards the family and towards society in a proper hierarchy of values.
233. Concerning the methods for practising responsible procreation, the first to be rejected as morally illicit are sterilization and abortion. The latter in particular is a horrendous crime and constitutes a particularly serious moral disorder; far from being a right, it is a sad phenomenon that contributes seriously to spreading a mentality against life, representing a dangerous threat to a just and democratic social coexistence.
Also to be rejected is recourse to contraceptive methods in their different forms: this rejection is based on a correct and integral understanding of the person and human sexuality and represents a moral call to defend the true development of peoples. On the other hand, the same reasons of an anthropological order justify recourse to periodic abstinence during times of the woman’s fertility. Rejecting contraception and using natural methods for regulating births means choosing to base interpersonal relations between the spouses on mutual respect and total acceptance, with positive consequences also for bringing about a more human order in society.
It is entirely possible that also Catholics in some parts of the world only follow some of the Church’s teaching in this regard. As a basic principle, the Church does not make its doctrines dependent on whether the majority approve or follow them. As far as the population numbers for those countries with Catholic majorities are concerned, looking at Latin America, the Philippines and Africa, for example, one cannot generalise that the population in Catholic countries is declining.