1 The Centenary of the promulgation of the Encyclical which begins with the words "Rerum novarum ", by my predecessor of venerable memory Pope Leo XIII, is an occasion of great importance for the present history of the Church and for my own Pontificate. It is an Encyclical that has the distinction of having been commemorated by solemn Papal documents from its fortieth anniversary to its ninetieth. It may be said that its path through history has been marked by other documents which paid tribute to it and applied it to the circumstances of the day. In doing likewise for the hundredth anniversary, in response to requests from many Bishops, Church institutions, and study centres, as well as business leaders and workers, both individually and as members of associations, I wish first and foremost to satisfy the debt of gratitude which the whole Church owes to this great Pope and his "immortal document". I also mean to show that the vital energies rising from that root have not been spent with the passing of the years, but rather have increased even more. This is evident from the various initiatives which have preceded, and which are to accompany and follow the celebration, initiatives promoted by Episcopal Conferences, by international agencies, universities and academic institutes, by professional associations and by other institutions and individuals in many parts of the world.
Source: Centesimus Annus (Vatican.va)