In 1994, the survey form stated that this variable may be reported by interviewer observation or by the respondent. In 1998, this variable was only reported from the respondent's answer; the survey did not use interviewer's observation. Responses from 1994 survey cannot be distinguished as either observer or self-report, as the survey did not capture this information.

In 1994, the Field Representative's Manual noted that if the residence was both on the 2nd and 3rd floor, then interviewers should indicate, "Basement, first or second floor." It further advises that residencies can only be considered on the third floor or above, "...if the entire residence is above the third floor."