23 Moreover, since the words of Christ "the harvest indeed is great, but the laborers are few" ( Matt . ix, 35; Luke x, 2) are true, even in the present condition of affairs, Europe from whence most of the missionaries have come is itself in need of priests, and this at a time when, with the help of God, it is most important that our separated brethren be led back to the unity of the Church and that non-Catholics be convinced of and delivered from their errors. It is a well-known fact that today the number of young men called to the priestly and religious life is not less than in former times, still the number of those who obey the call of God is certainly much smaller.
Source: Rerum Ecclesiae (Vatican.va)