Probably the most extensive research project which came to espouse a cultural explanation of demographic behavior was the Princeton European Fertility Project which examined the transition from high to low fertility occurring over much of late nineteenth and early twentieth century Europe. By using provincial-level data, the project set out to test several propositions of Demographic Transition Theory, one of which was that fertility declines were a consequence of economic development. A major conclusion of this body of research was that the observed fertility declines appeared to be only weakly related to conventional measures of socioeconomic development, such as the proportions in a province who were literate, employed in agriculture, lived in large cities, etc. In fact, in most European countries the fertility transition appeared to have begun at nearly the same time, despite considerable geographical variability in economic and social conditions. Hence, this too seemed to be a strong indication that the fertility transition was not an adaptive response to the changing conditions brought about by economic development. However, areas which shared similar cultural characteristics, such as language and religion, exhibited different rates of fertility change compared to areas at a similar economic level but with different cultural characteristics (Coale and Watkins 1986).