The degree of isonymy is greatly influenced by whether or not it includes the extent of isonymous relationship resulting from persons of the same surname living in the same residence. In a sample of 313 male citizens in one English village and 386 males in another village, isonymy within the same residence averaged 0.86. Total relationship by isonymy was 60% and 48% understated in samples of one individual of any surname at each residence in the two villages, such as would result from use of telephone directories as a source. In these villages isonymy between occupants of contiguous houses was also elevated. Only a small fraction of the total isonymy could be attributed to different residences on the same street, so this has little effect on the coefficient of relationship for the whole village or region. The larger the population, the less the bias from ignoring within-household relationships.
Lasker, Gabriel W.
"Brief Communication: Census versus Sample Data in Isonymy Studies: Relationship at Short Distances,"
5, Article 11.
Available at: https://digitalcommons.wayne.edu/humbiol/vol69/iss5/11