This paper brings data from ethnography, history, and family reconstitution to bear on the understanding of fertility differences and an early fertility decline under quasi-medieval institutions, in an area of Europe poorly known to demographers. Its theoretical intent is to sharpen the debate set by the general results of the Princeton European Fertility Project and critics of economic theories of fertility, from which sources one may draw the broad conclusion that economic factors are of lesser utility in explaining fertility differences and change, while cultural factors are more convincing.

Two points dominate the theoretical enterprise. The first shows the difficulty of using simple cultural or linguistic labeling as an explanatory device, but demonstrates the utility of economic explanation. The second shows that characteristics of political organization, working through control of economic resources, also had an effect on demographic behavior. Finally I propose that where ethnic labels are effective proxies, they are useful largely because elites have employed ethnic criteria to allocate sub-populations to positions in political and economic structures. Where the linkage between ethnic group definition and structural allocation is precise, ethnicity will proxy the underlying structural factors well and will serve as an explanatory device. Where distinctly different ethnic groups are allocated to similar structural positions, or where the same ethnic group is allocated to different structural positions, ethnicity will not proxy the structural factors well, with consequent loss of its explanatory power in the elucidation of demographic behavior.