Each survey collects the following employment information:

• a full work history of employment, including characteristics of the current or most recent employer and of any other employers for whom the respondent worked since the date of the last interview
• military service since the date of the last interview
• any gaps in employment since the date of the last interview

From this information and other retrospective information, a longitudinal record spanning from the date of, and to some extent the time preceding, the first interview through the most current interview date can be constructed for each respondent. The longitudinal record is maintained even for respondents who are not interviewed in interim years. Each year's questionnaire incorporates retrospective questions designed to recover as completely as possible information lost (or incorrectly reported or recorded) during previous survey years. 

For example, a respondent interviewed in 1984 and not interviewed again until 1989 will have a complete labor force history as of the 1989 interview, as information for the intervening period will be recovered in 1989. Researchers should be alert to the possibility of gaps and discrepancies in some records over time due to inconsistencies in respondent reporting or interviewer error. These inconsistencies have not appeared to be a major factor in the quality and completeness of the NLSY79 employment and labor force history.

The ability to link identical employers through survey years allows longitudinal examination of not only general labor force activity, but also employer-specific experience. Appendix 9: Linking Jobs Through Survey Years and Appendix 18: Work History Data both found in the NLSY79 Codebook Supplement, provide additional information. The Employer History Roster data, recently made available, provides other employer-specific characteristics.

Longitudinal Work Experience Record

This section discusses information on various aspects of the longitudinal work experience record available for each respondent of the NLSY79.

Number of Employers: The most basic longitudinal information available for respondents is the total number of employers for whom a respondent worked during a given period and the total number of employers (part-time and full-time) ever reported by a respondent. It is possible to construct fairly complete inventory of the number of jobs for all respondents from the age of 18 years and older; note the age effects discussion below.

"Employers" versus "Jobs": Unless explicitly noted, the NLSY79 work event history data are employer-based. Therefore, any reference to "job" is a reference to a specific employer. Information about specific duties and positions or changes in duties or position is collected, with reference to a specific employer, only at the point of interview (with limited exceptions in specific survey years). For example, a respondent may regard himself/herself as having held a number of "jobs" or positions with employer #1 (Job #1). However, any information collected about these different positions would be included as information about the respondent's experience with that employer (#1) at the point of interview for a specific year. Based upon this characteristic of these data, researchers are cautioned that counting changes in occupations can not necessarily be equated with total job changes or employer changes. For example, it is possible for a respondent to hold more than one occupation with the same employer during the time between interviews. Yet, except in restricted survey years, the only occupation specifically reported at the point of interview would be the current/most recent occupation. Likewise, a respondent may hold the same occupation through his or her tenure with several employers.

Effect of Age of Respondent on Employment Information: For those respondents who were 18 or older at the time of the first interview (1979), information about work history is recovered retrospectively to the age of 18. Information preceding this age may be relatively limited for these respondents. However, reported employers became part of the ongoing survey record of respondents who were younger than 18 at the time of the first survey. The depth of information for all jobs but the CPS job for respondents younger than 16 is somewhat restricted during the early survey years. Despite restrictions, a good deal of information is still available for those who were 15 years of age or under at the first interview point. More information on age restrictions is available in Employment: An Introduction (see Table 1 in that section).

Part-time versus Full-time Employers: If respondents report part-time or short-term employers who are not the CPS employers, there are restrictions on what information was gathered about industry, occupation, wages and class of worker. For a table of the universe restrictions, go to the section on Industries. This is also the case for year-specific modules, such as the 1990 promotion series. However, other basic information for part-time employers is available, such as start and stop dates, gaps within tenure with part-time or temporary employers, and hours worked per day and per week. In the event that a part-time/short-term employer is the CPS employer, complete data, including industry, occupation, and class of worker, are collected regardless of the nature of the job. Therefore, reasonable opportunity exists for comparisons of part-time/short-term and full-time employers, particularly if the part-time/short-term employer is the CPS employer.

Double-Counting of Employers: Users should be aware that a small degree of double-counting of employers may occur when data are collected. Until 1998 employers were only tracked between contiguous interview years in which information was collected on the specific employer. It is therefore conceivable that a respondent who works for a particular employer during one year, leaves that employer, and then returns to that same employer after a year or more, would appear to be working for a new employer during the second tenure because the previous tenure with that employer would have slipped out of scope for tracking purposes (see also the Jobs & Employers section). Starting in 1998, the NLSY79 began keeping a roster of all employers to enable the CAPI instrument to recognize when a respondent returns to an employer that they left a number of years earlier.

Despite some limitations, NLSY79 data allow for the construction of a relatively complete and detailed employment history for respondents from January 1, 1978 (and possibly points preceding), through the most current year in which a respondent was interviewed.

Tenure with Specific Employer

A second type of basic information that can be constructed from NLSY79 longitudinal labor force experience data is a history of tenure (in weeks) with each employer reported up to the most current survey year for a given respondent. Tenure excludes any unpaid within-job gaps. (see the Time & Tenure with Employer section for additional information).

A total tenure through contiguous survey years is available for all employers, full- and part-time, for whom valid start and stop dates of employment are reported. This is accomplished by linking identical employers through contiguous survey years; see Appendix 9 in the NLSY79 Codebook Supplement for more information. The construction of employer tenure occurs within the more expansive programming structure that produces the separate NLSY79 Work History data items. For more information on the consequences of missing start and stop dates, users should refer to the Work History section, which is devoted to a discussion of these data.

"Employer" Tenure versus "Job" Tenure:Researchers must be cognizant of the employer-based nature of these data (see the discussion above on "Number of Employers"). Tenure figures reflect time with a specific employer, not time performing a specific occupation with an employer. However, by using data on reported timing and nature of promotions present in two survey years for the CPS job and in 1990 for all jobs, it may be possible to impose some sense of change in occupations over certain periods of time.

Double-Counting of Employers and "Broken" Tenure: The limited possibility of double-counting of employers (discussed above) allows a slight chance of tenure with a single employer being calculated as tenure with two separate employers. An employer for whom the elapsed time between stints exceeds the capacity for continuous tracking will likely appear as two separate employers with two separate (and shorter) total tenure periods.

Gaps within Tenure with Specific Employer: Total tenure with an employer extends from reported start date to stop date. In addition, respondents may report gaps of a week or more during the period of association with an employer that fall within the period between start and stop dates. Unpaid gaps within tenure with the same employer are reported in association with a specific employer. They occur between the start and stop dates given for an employer. The respondent may not consider himself/herself completely disassociated from the relevant employer during these periods, although he or she was not actively working for that employer. Specific variables for each gap include start and stop dates; the reason that the respondent was not working during a given gap; the number of weeks that a respondent was unemployed (looking for work or on layoff) or out of the labor force (OLF or not looking for work) during a given gap; and, for those who were OLF at some time during a gap, the reason they were not looking for work.

Although a respondent may report himself or herself to be out of the labor force or unemployed during these gaps, these weeks are included in the calculation of total tenure with that employer because they occur before the respondent has reported an actual stop date for his or her association with that employer. Therefore, these weeks are considered part of the period for which the respondent considers himself/herself associated with that employer.

Users wishing to adjust total tenure with an employer to reflect such gaps must do so by calculating the length of reported gaps and eliminating them from the total tenure value. This can be done over the total of reported gaps or selectively, depending upon the reason or labor force activity classification (out of the labor force versus unemployed) of individual gaps.

Cumulative Labor Force Experience

For survey years 1979-1998 and 2006, the standard set of definitions of labor force status used by the Current Population Surveys (CPS) was used for coding the employment status of NLSY79 respondents "Labor Force Status." The NLSY79 Work History programs incorporate further refinements to allow for weeks of indeterminate status, due to erroneous respondent reporting or interviewer recording (see the Work History section). The NLSY79 summary indicators are then constructed, using these Work History definitions for weekly labor force status. The Labor Force Status section of this guide includes detailed definitions of CPS and NLSY79 Work History labor force concepts.

The detailed collection of dates of employment and gaps in employment over the history of the NLSY79 allows construction of a cumulative picture of a respondent's labor force activity over the course of the survey. A large number of summary variables are created based upon the week-by-week labor force status arrays produced by the Work History program (see the Work History and Labor Force Status sections for more information). These summary variables provide a count of the number of weeks a respondent held a given labor force status, the total number of hours worked (if any), and the total number of weeks since the respondent's last interview. Variables are also calculated indicating the percentage, if any, of weeks that are not accounted for in the summary variables discussed above, due to missing data or indeterminate status in the Work History arrays.

These variables, constructed within the Work History programs, consist of two sets. One series uses "Last Interview Date" as the reference period, and the second uses "Past Calendar Year" (the full calendar year previous to the year of current interview) for its summations. However, it is possible to construct similar cumulative figures for periods of time of particular interest to them. For instance, one may be interested in compiling a summary of work or labor force experience for respondents over a specific five-year period. Similarly, a summary of activities with employers having certain characteristics (part-time, temporary, full-time, CPS, certain levels of earnings, and so forth), as well as the extent of such practices such as dual job holding among respondents, may be compiled. A gaps history can also be assembled using, as appropriate, gaps reported within the tenure with an employer or gaps where no employer affiliation is reported.

Cumulative Active Military Service: Cumulative weeks of active military service are constructed during the creation of the NLSY79 Work History data set. However, civilian employment has precedence over military activity in the week-by-week labor force status arrays. Therefore, the number of weeks in active military service in the past calendar year will not include any weeks during which the respondent also held a civilian job. The full period of active military enlistment can be verified by using data on enlistment and discharge dates from the actual military section in the main questionnaire. The number of weeks in the active military since the last interview is calculated by subtracting the starting week from the ending week so that the entire tenure is included.

Gaps between Employers (No Affiliation with an Employer): As mentioned, gaps may be reported between the start and stop dates for a given employer, reflecting periods for which a respondent considers himself or herself affiliated with an employer but not actively working. In addition, gaps in employment reflect periods when the respondent reported no affiliation with any employer. These gaps are often referred to as "between-job gaps."

Indeterminate Labor Force Status during Gaps: The exact duration of gaps in weeks (within-job gaps or between-job gaps) is available, as well as the number of those weeks the respondent was "out of the labor force (OLF) - not looking for work" as opposed to "unemployed - looking for work or on layoff." Therefore, if a respondent was  unemployed for the entire period of the gap, the specific weeks for those labor force statuses can be determined. However, for a gap in which the respondent was OLF part of the time and unemployed part of the time, the specific weeks that the respondent occupied each status cannot be determined.  Researchers should be aware that, while the number of weeks the respondent occupied each status is accurate, the precise weeks for each status may not be. The Work History Data section provides details on the assignment of non-employed labor force status.

Weeks with Indeterminate Activity: Users should be aware that, under some circumstances, it is not possible to determine labor force status for a given week. These indeterminations arise with incomplete or invalid start or stop dates for employers or gaps. For example, an element of the date is missing or the stop date precedes the start date. Variables reflecting the percentage of weeks that were unaccounted for since the last interview and in the past calendar year are computed. Hence, users may find respondents who worked 52 weeks of the year but also have 100 percent of their weeks unaccounted for. These variables alert researchers to problem cases that may need to be examined more closely or eliminated from analysis. The Work History Data section provides additional information.

Employer Characteristic Histories: It is possible to build a limited history of certain employer-based characteristics (earnings/hourly wages, occupation, and so forth). These histories will be limited in the sense that many of these characteristics are reported only at the date of each interview.  Should change occur from one interview date to another, the point of actual change cannot, in most instances, be precisely determined. (Information collected in select survey years may permit more definitive identification of interim changes occurring between interview dates for certain characteristics.) 

Strictly speaking, it is possible that an occupational change from one interview year to the next could reflect only one of several during the period between interviews. Characteristics such as hourly wage may be of less concern in this regard, as some numeric progression or regression should be apparent. Even for these indicators, interim and temporary cutbacks in compensation in times of economic downturn may be missed. Noting these limitations, it is possible to construct a reasonably complete history of experience with specific employers, such as CPS employer or all employers.

CPS Employer as a Primary Focus: The CPS employer (current/or most recent at date of interview) is the focus of many researchers. These employers can be linked in much the same way as non-CPS employers, with one extra set of variables identifying the employer as CPS. However, it is important to note that, while the CPS employer is usually the first employer, this is not always the case in survey years 1980-92. 

Discrepancies in the order in which interviewers administered, or respondents reported, employers for Employer Supplements resulted in a relatively small number of cases in each pre-CAPI survey year for which the CPS is not the first employer, but rather Job #2 or Job #3, etc. The CPS employer can be identified in each year by a "yes or no" variable, which is present for each employer. A "1 - yes" code indicates the CPS employer. It is possible that an employer that is the CPS employer in one year and remains the CPS employer in the next year will be Job #1 in the first year and Job #2 (or higher) in the second year. In this case, the information for Job #2 in the second year would be a continuation of the information for Job #1 in the first survey year. While in 1979 Job #1 is always the CPS job, in 1993 and after, the CAPI instruments ensure that the CPS job (if one exists) will always be Job #1.

Comparison to Other NLS Cohorts: Total number of weeks worked and total weeks of tenure variables have been constructed for each cohort. For more precise details about the content of each survey, consult the appropriate cohort's User's Guide using the tabs above for more information.