The figures given here for the Catholic Church globally come mainly from CARA (Center for Applied Research in the Apostolate) based at Georgetown University, USA and Agenzia Fides, the information service of the Pontifical Mission Societies, based at the Vatican.
The figures for the Catholic Church in Ireland come from the Irish Catholic Bishops Conference.
N.B. While statistics have their use in giving us an idea of the physical and numerical state of the Church today and over time, they are not to be relied upon to give a true and definitive diagnosis of the health of the Church at any given time. The Church likes to have high numbers because Her Divine mission is to bring all souls to Christ. However, the Church prefers quality rather than quantity, both in the ranks of the clergy and religious, as well as among the ordinary laity. It is certain that, while there is physical growth in certain areas of the Church, there are serious grounds to fear that the quality that the Church has always looked for does not match the quantity. This quality has two elements: (a) absolute fidelity to the constant and traditional teaching of Christ through His Church and (b) a high level of compliance with this teaching in the lives of those who hold the Faith (i.e. holiness or sanctity). The first element is in a sense more important because “without Faith we cannot please God”. Also, true holiness depends on doctrinal integrity because we cannot truly love what we do not know and because, if we want to accept Christ as He really is, we cannot reject any of His teachings. On the other hand, Faith on its own is not enough, but must lead us to Charity – love of God and love of our neighbour for His sake.