The Princeton Project on the Decline of Fertility in Europe (or European Fertility Project, hereafter EFP) was carried out at Princeton University's Office of Population Research in the 1960s and 1970s. This project aimed to characterize the decline of fertility that took place in Europe during the nineteenth and early twentieth centuries. The project's summary statements argued that social and economic forces played little role in bringing about the fertility transition. The statement stresses instead a process of innovation and diffusion. A central feature of the EFP argument is a series of statistical exercises that purport to show that changes in economic and social conditions exerted little influence on fertility. Two recent papers on Germany for this period have used similar data and methods to draw different conclusions. These findings echo those of researchers working in other contexts, who increasingly find that economic and social factors play a strong role in fertility. We show that one reason for the new findings is some general statistical problems in the Princeton methodology. These are reason to temper acceptance of the Princeton project's larger message.