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Andorra, one of the smallest countries in Europe, is geographically very isolated. Located in the Central Pyrenees, it is surrounded by high mountains. This paper investigates the endogamous levels and relationships between demographic or geographical variation and inbreeding coefficients calculated through isonymic methods. Our results suggest that political and geographical frontiers are not significant enough to pose effective genetic barriers. The overall inbreeding coefficient average (0.0031) is moderate with respect to other populations in the same region. Temporal and geographical variations of total inbreeding and their components are explained in relation to changes in population size and intensity, and to origin and destination of migrant collectives. Although the spatial distribution of the population of Andorra is the main contributing factor to inbreeding, the kin-structured composition of immigrant collectives is another fundamental factor that helps to explain the levels and variation of inbreeding.