St. Ambrose, a Doctor of the Church, was influencial in explicating the high edeals we have in the Church concerrning consecrated chastity. People mocked him, saying that the world would be depopulated if all followed his teaching. St. Ambrose responded by asserting that the population increases in direct proportion to the esteem in which virginity is held.
That is an amazing statement. Can it really be true? Of course, and we need only look at our current world. Pockets of immorality such as California have a higher death rate than birth rate not because of high crime, but because of abortion and contraception. France is even worse, and yet their population is not falling. This is because the number of Muslims immigrating to the country more than make up the difference. France is slowly becoming a Muslim country because of the immorality of its people.