Relationships between consanguinity and migration rate from surname distributions and isonymy in France.

ABSTRACT

The distribution of surnames in France during the period 1916-40 is analysed from the civil birth registers for each of the 36,500 administrative units. The migration rate estimated from surnames is compared with the migration rate obtained from demographic census data. The correlations calculated among the 90 Departments ranges between 0.52 and 0.76 according to the size of the communes. Moreover, the migration rate is shown to be highly correlated with the average coefficient of consanguinity based on dispensations for marriages between relatives. These findings point to the validity and the usefulness of quantifying migrations on the basis of surname data and they show that migration flux and consanguinity are inversely and closely linked.