The use of parish marriage registers in biodemographic studies: two case studies from 19th-century Italy.

No previous studies have critically evaluated the representativeness or reliability of parish marriage registers for biodemographic studies of historical Italian populations. Because of the widespread Italian custom of spouses settling down in the groom's parish after getting married in the bride's, such registers do not contain any information on wife-exogamous unions. This fact affects not only the number of marriages considered, but also any estimates of the biodemographic parameters usually assessed in these types of studies, especially when open populations are considered. Due to the richness of the parish archives for two populations in central Italy, it was possible to retrieve from the Status Animarum (Register of Souls) information concerning the missing data regarding marriages. Consequently, it was possible to compare values of marital structure indices obtained using only data from marriage registers with the corresponding figures computed using either the complete data series of marriages or solely that of resident couples. The results demonstrate the existence of significant variations in the figures for the exogamy rate, as well as in the number of new family names introduced by marriage. In addition, F and RP values showed important but nonhomogeneous variations.