Are Voluntarily Unlisted Telephone Subscribers Really Different?

Telephone surveys are widely employed because of their speed and low cost, but the problem of whether listed telephone subscribers are representative of unlisted subscribers is an aggravating one to researchers. If unlisted subscribers are different, what are significant? Surprisingly, the literature sheds little light on this question, and researchers are forced to assume that differences, if any, are not significant. In 1965 Kildegaard reported that the differences between telephone and total populations are becoming less distinct.. . but also opined that there were dependent upon geographic region, income, age of household head, and urban/nonurban residence 2. Such difficulties may be compounded if, in fact, there are also between characteristics of listed and unlisted subscribers. Some researchers indicate that the size of the unlisted subscriber universe is not inconsequential. Cooper reported in a study of greater Cincinnati that nine percent had requested unlisted numbers 1. In the present study, conducted during the first quarter of a telephone directory year, approximately 13% of the subscribers requested that their numbers be unlisted.