An unlisted household is a residential unit that does not have a telephone number listed in published directories or one that would be given out by directory assistance. A telephone number may be unlisted for several reasons. Household residents actively may have chosen to keep their telephone number unlisted. Alternatively, although the residents of an unlisted household may not have specifically chosen to keep their telephone number unlisted, the number may be too new to be found in published directories or via directory assistance. This can be a result of a recent move or change in telephone number.

Although the literature suggests important differences between the characteristics of respondents who choose to keep their telephone numbers unlisted and respondents whose telephone numbers are unlisted for other ...