What caused fertility variations by settlement in Transylvania at the time of industrialization?

Previous research results regarding Hungary could not show the effect of some socio-economic variables on fertility, due to the high level of aggregation. They favoured cultural explanations, and shown Hungary as an exception to the rules of demographic transition. In contrast, this paper shows that the classic explanatory factors like infant mortality, migration, literacy, and secularization do explain fertility differentials in Transylvania at the turn of the 20th century.