Interview Methodology

• Interview schedule and fielding periods
• Interview methods and target universe

Interview schedule and fielding periods

In the initial survey plan, respondents from each of the four Original Cohorts were to be interviewed yearly over a five-year period. Due to cost considerations, it was decided after the second survey of the Older Men to survey the two older groups (Older Men and Mature Women) biennially rather than annually. Due to their greater mobility, the Young Women and Young Men were interviewed annually.

A decision was made at the end of the first five-year period to continue the interviews for another five years because of the usefulness of these data and the relatively small sample attrition. At this point, the interviewing pattern changed to a 2-2-1 schedule; each respondent was contacted by phone approximately every two years, then again in person one year after the second phone interview. The 2-2-1 schedule was continued through 1981 for the Young Men and 1983 for the Older Men, when interviewing of both cohorts ceased. The Older Men or their proxies were then personally reinterviewed in 1990.

Tables 1a and 1b depict the years in which each cohort was surveyed, the type of interview used, the fielding period, and the number and percent of respondents with completed interviews.

Interview methods and target universe

Listings of respondents to be interviewed were generated by the Census Bureau and distributed to its 12 regional offices. Current addresses and contact information were generated from information on the various Household Record Cards as well as through a postal check conducted by Census. Cases were assigned to interviewers who lived in the same geographic area as the respondent. For each respondent in their caseload, interviewers received copies of the questionnaire, respondents' Household Record Cards, flashcards, and information booklets.

Interviewers were responsible for contacting each respondent in their caseload and for using additional local resources to locate respondents who had moved since the last interview. Respondents who had moved outside the geographic district of their original interviewer were assigned another interviewer unless there was no interviewer nearby. In the latter event, an effort was made to interview the respondent by telephone.

Each respondent to be interviewed was sent various materials designed to encourage continued participation. Advance letters thanking respondents for their continued participation and informing them of the coming survey were mailed prior to each interview period. Fact sheets highlighting recent research findings from each cohort's survey data were also provided. Respondents who initially refused to participate in a survey were sent refusal letters by the regional offices designed to encourage their continued participation and were once again contacted by local level interviewers to secure the interview.

While the type of survey, personal or telephone, determined the chief mode of contact, an alternate contact method was used for certain respondents. During a personal survey, for example, those respondents who lived long distances from the Census interviewer's base of operation or those for whom the Census supervisor decided that another contact method was warranted were contacted by telephone. Although survey instruments are written in English only, multilingual interpreters were made available by the regional offices to interviewers who needed them.

The average length of an interview varied depending on the type conducted, with personal interviews lasting from 50-60 minutes and telephone interviews averaging 20-25 minutes. No stipends were paid to respondents in the men's cohorts for their participation in the NLS.

Respondents selected for interviewing each year were, with the exceptions noted below, those who had participated in the initial year interviews and who were alive, living within the United States at the interview date, and noninstitutionalized. Subsequent to the first year interview for each cohort, those respondents who had refused to be interviewed were dropped from the sample; respondents who had been noninterviews for reasons other than death or refusal for two consecutive years were also eliminated from attempted interviewing. This noninterview exclusion was not applied to those members of the Young Men cohort who were subsequently inducted into the Armed Forces. No interviews were attempted with this group while they were on active military duty. They were, however, retained in the sample and attempts were made to reinterview them as soon as they left active military service. Table 2 depicts reasons for exclusion from the eligible samples.

Survey design and fielding procedures for the 1990 Older Men resurvey differed substantially from those employed during earlier interviews. Respondents in this cohort were last surveyed in 1983 and, if living, would have been between 69 and 83 years of age at the time of the 1990 interviews. It was expected that nearly half of the original cohort members could be deceased by the time of this resurvey.

The goal of the 1990 interviews was expanded to include obtaining information about the original cohort member regardless of his ability to respond. Questionnaires were designed for interviews with not only respondents, called "sample persons" for the purposes of this survey, but with widows of deceased sample members, or other next-of-kin in the absence of a widow. Information was to be collected not only on the labor market activities, retirement experience, and health of the respondent, whether living or deceased, but also on the widow's work experience, household composition, and family income. Institutionalized sample persons or widows--those who resided in nursing homes, homes for the needy, mental institutions, correctional facilities and long stay hospitals--were to be interviewed. Staff members at institutions could be contacted to provide information on residency within and medical insurance coverage for long-term care facilities. To assess cognitive functioning, e.g., orientation to time and place, long-term memory, and arithmetic ability, the Short Portable Mental Status Questionnaire (SPMSQ) was administered to all sample persons and widows.

Proxy interviews were encouraged in cases where the sample person was physically or mentally unable to participate. Eligible proxies, in order of preference, included a sample person's wife, child, relative, friend, or neighbor, with those residing with or close to the respondent (e.g., in the same household, in the same community) preferred over those living some distance away. Finally, Census address information, which had last been updated in 1983, was supplemented by locator information from the Social Security Administration for both sample persons and their beneficiaries. These unusual procedures resulted in some information being collected from or about 4,298 (86%) of the original cohort members. Interviews were completed with 2,092 original sample persons (90% of those designated by Census as alive in 1990) and with 2,206 respondent widows or other next-of-kin (82% of those designated deceased before the interviews began). Table 3 summarizes response rates and types of interviews for the 1990 resurvey.