9 This exhortation of Benedict XV, which was repeated by Our predecessors Pius XI and Pius XII, with the help of God's divine Providence has had visible and copious results. We want you to join Us in rendering thanks to God for the fact that a numerous and elect legion of bishops and priests has arisen in the Mission territories, Our brethren and beloved sons, who fill Our heart with great expectations. If We cast even a cursory glance on the ecclesiastical situation in the areas which are entrusted to the Sacred Congregation for the Propagation of the Faith, with the exception of those at present under persecution, We note that the first bishop of east Asian origins was consecrated in 1923, and the first vicars apostolic of African Negro descent were named in 1939. By 1959, We count 68 Asian and 25 African bishops. The remaining native clergy grew in number from 919 in 1918 to 5553 in 1957 in Asia, and during the same period in Africa from 90 in 1918 to 1811 in 1957. With such an admirable increase in the numbers of the clergy did the Lord of the harvest (l6) desire to reward adequately the labors and merits of those who zealously did mission work, either individually or in cooperation with many others, responding with a generous heart to the repeated exhortations of this Apostolic See.
Source: Princeps Pastorum (Vatican.va)