4.1 Age

This section discusses the age and date of birth variables associated with NLSY79 respondents.  In addition to the respondent-specific variables discussed in this section, information is also available on the age and/or date of birth for other household members; see the "Household Composition" section for details.

Date of birth information was collected from each NLSY79 respondent during the 1979 and 1981 interviews.  The variable ‘Age of R,’ gathered during the 1979–83 surveys, is the self-reported age of the respondent as of the interview date.  The NLSY79 main data files also contain a yearly created variable, ‘Age of R at Interview Date.’  These created variables are constructed using the 1981 date of birth information coupled with the 1979 birthdate for the 491 respondents not interviewed in 1981.

Table 4.1.1 Age & Date of Birth Variables for Respondents: NLSY79 (1979-2004)

Users should note that age of respondent variables from the Supplemental Fertility File (area of interest “Fertility and Relationship History/Created”), including ‘Age of R at 1st Birth’ and ‘Age of R at Start of 1st Pregnancy,’ have been constructed using the 1979 date of birth information. 

Table 4.1.1 presents the reference numbers and areas of interest in which the more commonly used age variables can be found.  Tables 4.1.2 and 4.1.3 depict age distributions of the NLSY79 for the 1979–2004 survey years.  The first table uses the created variable ‘Age of R at Interview Date.’

Table 4.1.2 Age Distribution of Respondents on Day of Interview (Unweighted Data)

Table 4.1.3 Age Distribution of Respondents on June 30th of Interview Year (Unweighted Data)

Survey Instruments & Documentation: Questions regarding age of the respondent are located in Section 1 of the 1979 through 1983 questionnaires.  Date of birth questions are printed in the first section of the 1979 and 1981 instruments.  Age-related questions for family members are located in the 1978 Household Screener and, for subsequent years, on the Household Interview Forms.

Data Files: The 1979 and 1981 birth date variables have been placed, respectively, in the “Family Background” and “Common” areas of interest on the NLSY79 main data set.  The 1979–83 age variables are located in “Family Background.”  The series of created age variables can be found in “Key Variables.”  The Supplemental Fertility File age variables can be found in the “Fertility and Relationship History/Created” area of interest.  Age information for NLSY79 household members can be found in the “Household Record” area of interest.

Inconsistencies in age and/or birth date information may appear for a number of reasons:  (1)  Age and birth date information has been collected at multiple survey points, giving rise to respondent-reported inconsistencies; (2) respondents’ ages for sample selection were based on date of birth information reported at the time of the 1978 household screening by individuals who may not have been the respondent; and (3) responses to interviewer check items, i.e., the age reported to the interviewer that determines when age-specific questions should be asked, may not be the same age as that calculated from previously reported age or birth date information.  For example, a respondent whose age was 16 as calculated from the birth date reported in 1981 may have answered questions which were specific to a 17 year old.  When analyzing age-related questions, the user may wish to review the birth dates as reported in 1979 as well as in 1981 if inconsistencies arise.  It should be noted that eligibility for inclusion in this cohort was based on the 1979 age reports, as are weights.

Age Restrictions on Early Work Experience Data: In the early survey years, some restrictions were imposed on data collected on work experience, specific employers, and military service.  These restrictions applied, for the most part, to those respondents under the age of 16 at the time of the 1979 survey, although some extend beyond that age.  The following is a summary of age restrictions that can be found in the work and job experience sections of the 1979 questionnaire:

"Section 6-On Knowledge of and Experiences with the World of Work”:  Respondents who were 14–15 years old were skipped out after questions asking them their thoughts on certain kinds of jobs that people actually do, i.e., skipped out at Q.2.  These questions are found in the “Attitude” area of interest.

“Section 7-Military”:  Those respondents 16 years and under at the 1979 and subsequent interviews were skipped past all military service questions.  This age group was only asked three questions concerning attitudes on service in the military and the possibility of enlistment in the future (Q.72–Q.74).  Variables from this section are found in the “Misc. 1979” area of interest, and for subsequent years, in both the “Misc. xxxx” and “Military” areas of interest.

“Section 8-On Current Labor Force Status (CPS Questions)”:  Those CPS questions concerning activity most of the survey week and CPS job (Q.1–Q.36) were asked of all respondents.  However, those respondents ages 15 or younger were not asked the questions dealing with looking for work.  Questions in this section are found in the “CPS” and “Misc. xxxx” areas of interest.

“Section 9-On Jobs”:  Information on school-related jobs is collected for 14- and 15-year-olds.  School-related job information is also collected for other respondents who were not employed since 1978 and who were enrolled in regular school at some time since January 1, 1978.  For those 16 years and older, information on all jobs since January 1, 1978, was collected.  For all respondents, information was gathered on enrollment in various types of government-sponsored programs that provided jobs.  These variables can be found in the “Jobs” and “Misc. 1979” areas of interest.

"Section 10-Jobs" (Employer Supplements, in subsequent survey years): Each job could be coded with one or more of the following:

• "If this job was part of R's school program, circle code "2" here"
• "If this job was part of a college work-study program, circle code "3" here"
• "If this job was a part-time job provided by the government, circle code "4" here"
• "If this job was a government-sponsored summer job, circle code "5" here"
• "If this job was part of a government-sponsored program for people not attending regular school, circle code "6" here"
• "If this job was part of any other kind of government-sponsored program, circle code "7" here"

If codes 4–7 above were circled, the job was identified as some type of government-sponsored job or government program providing a job.  Respondents were asked the same questions about government jobs that they were asked about non-government jobs.  However, an additional series of questions was asked about jobs identified as government-sponsored by one of the above codes.  Jobs that were school-related/work-study programs can also be identified by the first two codes listed above.

For the first job listed (which should be the CPS job), 14–15 year olds were routed through the entire series of questions, whether or not the job was a government-sponsored job.  For each additional job that was not government-sponsored, 14 and 15 year olds were asked only a basic set of questions about start/stop dates, reasons for leaving (if applicable), and hours worked per week.  For each additional job that was government-sponsored, all applicable information was gathered, regardless of the age of the respondent.

These variables can be found in the “Job Information,” “Government Jobs,” and “Misc. 1979” areas of interest.  Users should keep in mind that some of the information contained in the “Job Information” variables will refer to government-sponsored jobs (and possibly school-related/work-study jobs), as general information was collected on these jobs as well.

“Section 11-On Last Job Lasting 2 Weeks or More”:  Information is regularly collected on the last job held.  There is no age restriction.  These questions can be found in the “Jobs before 1978” area of interest.

“Section 12-On Work Experience Prior to January 1, 1978”:  If the respondent was 19 years or younger at the time of the 1979 interview, he or she would have been under 18 before 1978, so the retrospective information for the time period prior to 1978 was not collected.  However, respondents not enrolled in regular school at any time between January 1978 and the interview date, regardless of age, were asked about the first job they held for two or more months at which they worked 20 hours a week or more after they stopped attending school.  Variables from this section are found in the “Jobs after School” area of interest.

“Section 13-On Government Training”: All respondents enrolled in grades 1–12 are skipped over this entire section.

Comparison to Other NLS Cohorts: Age data are available for all NLS cohorts.  These variables include both the age of the respondents as of a fixed date during the initial survey year and as of the interview date in various years.  Date of birth is also available for all cohorts.  Consult the BLS website at http://www.bls.gov/nls or the appropriate cohort’s User’s Guide for information about accessing these data.