Isonymy in emigrants from Ferrara in 1981-1988.

The distribution of surnames in the emigrants from the population of the town of Ferrara in the period 1981-88 was studied by sex and place of birth, namely Ferrara versus other places. Emigrants born in Ferrara were defined as first time emigrants and those who had previously immigrated to Ferrara were defined second time emigrants. It was found that random isonymy is smaller in second time emigrants. Sex ratio is not different in the two types of emigrants. As indicators of the abundance of surnames in a distribution, the common ecological indexes derived from entropy were used and compared between types of emigrants. It was found that redundancy, as isonymy, is larger in the first time emigrants than in second time emigrants. It was observed that second time emigrants were consistently and significantly older than first time emigrants, and that a considerable fraction of them, (22.4%) returned to their place of birth. A sexual dimorphism in age at emigration was observed in second time emigrants, females emigrating at an older age than males.