Terrible figures

The ecclesiastical prohibition of mixed marriages is so obviously made clear and substantiated by the statistics that it almost requires presumptuous confidence to enter into a mixed marriage anyway.
Mixed marriages in the Reich.
Between 1923 and 1927, a total of 291,481 mixed marriages took place in the German Reich (including the Saar region). For every 100 Catholics who married, an average of 18.57 entered into a mixed marriage in this five-year period. Of the 291,481 mixed marriages, 180,118, i.e. 61.79 percent, did not marry in church. This is practically equivalent to 180,118 Catholics leaving the Church. However, the main victims of mixed marriages are the 195,911 children who were deprived of baptismal grace in the aforementioned 5-year period through the fault of the Catholic parent. We lost 376,029 souls in marriage and baptism losses in the 5 years, i.e. an average of 75,000 souls per year.
Mixed marriages in the diaspora.
Our diaspora communities are proportionally the most afflicted and thinned out by intermarriage. Fr. Krose SJ. gave a statistical description of church life in the diaspora in contrast to the Catholic homeland for the year 1926 in the priestly yearbook of the Boniface Association [Bonifatiusverein] (1929). In the diaspora, more than half of all marrying Catholics, namely 54.7 percent, entered into a mixed marriage, compared with only 7.1 percent in Catholic areas. 70.3 percent of mixed marriages in the diaspora did not include a church wedding, compared with 49.6 percent in the hinterland. Only 42.6 percent of mixed-race children in the diaspora are baptized, compared with 59.5 percent in the Catholic region.
Do mixed marriages solemnized in the Church succeed?
Statistical observations in the province of Saxony in the prewar years showed that 97 percent of the mixed marriages that were solemnized in the Church had their children baptized Catholic. The situation was worse for the Catholic upbringing of these children of mixed marriages. The curse of mixed marriages comes upon the children, despite the otherwise good will of all parties. They are increasingly lost to the Church in the following generations, namely 25 percent of the first generation, 50 percent of the second generation and 82 percent of the third generation of children of Catholic mixed marriages. In the fourth generation, hardly any significant Catholic part remains. This dilutes the Catholic blood in mixed marriages.

The divorce rate of mixed marriages.
The inner impossibility of mixed marriages is revealed in the high divorce rate. On average, for every 1000 existing marriages in Prussia between 1905 and 1913, there were 0.5 divorces in purely Catholic marriages, 1.5 divorces in purely Protestant marriages and 3.4 divorces in mixed marriages. This means that mixed marriages were almost seven times more likely to end in divorce than purely Catholic couples. In Berlin, 942 Catholic marriages were divorced in 1928. Of these 942 dissolved marriages, 243 were purely Catholic and 699 were mixed. The unnatural nature of mixed marriages leads to an external catastrophe. Mixed marriages lack a firm foundation, an intimate community. Moreover, Protestants do not recognize the indissolubility of marriage. If they divorce, the Catholic spouse remains bound. A mixed marriage is and remains a mixed marriage, a misfortune for the spouses and the children. The Church condemns mixed marriages not only in the protection of her rights, but even more in the faithful care for the faith and the happiness of her children. More pagans than Christians grow out of mixed marriages. That is why even devout Protestants warn against it. A well-known Protestant theologian says: “Consciously Protestant Christians and convinced Catholics will hardly enter into a mixed marriage. Strong religious personalities are more likely to renounce marriage than religious communion in marriage. No church that believes itself to be in possession of eternal truth can remain indifferent to the proliferation of mixed marriages and the alienation of offspring. No one will deny the churches the right or the duty to influence their members to refrain from mixed marriages.”
(From the “Bonifatiusblatt”, 1931, issue 3.)