In his recent study,The Decline of Fertility in Germany, 1871–1939, John Knodel shows that in about two generations the ‘overall fertility declined by 60 percent, marital fertility by 65 percent, and illegitimate fertility by 54 percent.’ Given the facts that a greater percentage of women of child-bearing ages than ever before were married during this period, and that illegitimate births never counted for more than 10 percent of the total births, Knodel concludes that the decline was mainly due to a reduction of marital fertility. This decline became apparent in the 1870s and was already pronounced enough to be a matter of concern for a variety of sociologists, demographers, and physicians in the decades immediately before the First World War. One of the reasons for this contemporary concern sprang from the belief that the secular decline in fertility indicated that birth control, hitherto presumably limited to the effete French and to rather small numbers of German middle class and professional families, was now being practiced with a marked degree of success by large numbers of German working class families. In the minds of many nationalistic demographers, what had been the private vice of the publicly virtuous now threatened to become a mass phenomenon with potentially disastrous results.