Types of Variables

Types of Variables
There are six types of variables present in the NLSY79 data. Some are the raw answers provided by the respondent, while others are constructed. Types of variables include:
- Direct (or raw) responses from a questionnaire or other survey instrument
- Edited variables constructed from raw data according to consistent and detailed sets of procedures, such as occupational codes, KEY variables, and so forth
- Constructed variables based on responses to more than one data item, either cross-sectionally or longitudinally, and edited for consistency where necessary, such as variables on the NLSY79 Supplemental Fertility File (''Fertility and Relationship History/Created'' area of interest in NLS Investigator)
- Constructed variables from other sources, such as the County & City Data Book information present on the NLSY79 Geocode data files
- Variables provided by an outside organization based on sources not directly available to the user, such as the high school survey and transcript data, scores from the Armed Services Vocational Aptitude Battery, and so forth
- Data collected from or about one universe of respondents reconstructed with a second universe as the unit of observation, such as variables on the NLSY79 Child File
The type of variable impacts:
- the title or variable description naming each variable
- the physical placement of each variable within the codebook
- the location of a variable within a given area of interest
Reference Numbers
Every variable in the main NLSY79 data files has been assigned a reference number or identifier that determines its relative position within the data file and NLS documentation system. Persons contacting NLS User Services should be prepared to discuss their question or problem in relationship to the reference number(s) of the variable(s) in question.
Important Information
In general, the Center for Human Resource Research does not impute missing values or perform internal consistency checks across waves. Exceptions to this general rule occur when financial support is available, as is the case with the consistency edits performed since 1982 on the NLSY79 fertility data. When bounded interviewing methods are used, responses from the previous interview appear in the text of a question, both to verify that past information and as a point from which to update current information. Bounded interviewing techniques, using data from the Information Sheets or flap items, are intended to impose consistency across waves. Data quality checks most often occur in the process of constructing (1) cumulative and current status variables, such as 'Highest Grade Completed,' and (2) NLSY79 employment-related variables, such as 'Weeks Working in Past Calendar Year,' 'Total Tenure with Employer,' and so forth. More information on NLSY79 instruments can be found in the Survey Instruments section.
Once assigned to variables within the NLSY79 data files, reference numbers remain constant through subsequent revisions of the files. Reference numbers are assigned sequentially, with variables referring to the first survey year having a lower reference number than those variables specific to the second year and so forth.
Occasionally variables are created in a year later than that in which the data were actually collected. These variables are frequently given a reference number with a decimal value that reflects the year in which the actual data were gathered rather than the year the created variable was constructed, for example, R01461.01. Beginning with the 1993 survey, decimals are also used to indicate that more than one variable has been derived from a single question.
Important Information
Reference numbers in the main and Geocode data files have traditionally begun with the letter'' R.'' Beginning with the 2000 data release, the work history variables are incorporated with the main data on the same data set. However, these work history variables are assigned reference numbers beginning with ''W'' for easy identification. Beginning in 2006, government program participation or recipiency variables are assigned reference numbers beginning with ''G'', health module variables are assigned reference numbers beginning with ''H'', and all other variables are assigned reference numbers beginning with ''T''.
Variable Descriptions or Variable Titles
Each variable within NLSY79 main file data files has been assigned an 80 character summary title that serves as the verbal representation of that variable throughout the documentation.
Variable titles are assigned by CHRR archivists who endeavor, within the limitations described below, to capture the core "content" of the variable and to incorporate within the title:
- "NLS Investigator areas of interest" that facilitate easy identification of related variables
- "Universe identifiers" that specify the subset of respondents for which each variable is relevant
- for some variables, "Reference periods" that indicate the period of time, such as survey year or calendar year, to which data refer. Universe identifiers and reference periods are discussed below.
Universe Identifiers. If two ostensibly identical variables differ only in that they refer to different universes, the variable title will include a reference to the applicable universe by either appending in parentheses to each title the appropriate universe (Example 1) or by identifying the universe before the variable title (Example 2).
Example 1: 'Did R Have Any Job since Last Int? (Unemployed or OLF) (1994)'
Example 2: 'Female - Number of Children R Has Had since Last Interview'
Reference Periods. Variable descriptions may include a phrase indicating the time period to which the data refer. When a date follows a verbal description of a variable and is preceded by the prepositional phrase ''in 19XX,'' the date identifies the calendar year for which the relevant information was collected.
Example: 'Received Income from Child Support in 1991?' This 1992 survey question refers to child support payments received in calendar year 1991.
Important Information
Do not presume that two variables with the same or similar titles necessarily have the same (1) universe of respondents or (2) coding categories or (3) time reference period. While the universe identifier conventions discussed above have been utilized, users are urged to consult the questionnaires for skip patterns and exact time periods for a given variable and to factor in the relevant fielding period(s) for the cohort. In addition, variables with similar content may have completely different titles, depending on the type of variable (raw versus created).
Variables with similar content, such as information on respondents' labor force status, may have completely different titles, depending on the type of variable (raw versus created). In addition, such variables may be located within different NLSY79 areas of interest.
Example 1: 'Employment Status Recode' (ESR), in 1979-98 and 2006, is the created or reconstructed version of the 'Activity Most of Survey Week' raw variable. The 'Activity' variable is derived from the first question of the full series of questions used by the Department of Labor (DOL) to obtain employment status; the title reflects questionnaire content. ESR, on the other hand, reflects the procedure used to recode the 'Activity' variable. This produces a constructed variable for all respondents based upon responses to the 'Activity' question and all other questions used by the DOL to obtain employment status. These other questions serve to qualify and refine employment status beyond the answer to the initial 'Activity' question.
Example 2: NLSY79 raw fertility variables appear within the various ''Children,'' ''Birth Record'' or ''Birth Record xxxx'' areas of interest while edited and constructed versions of these variables appear within the ''Fertility and Relationship History/Created'' area of interest.
Finally, different archivists, for a period of more than 20 years, have performed the task of assigning variable descriptions to data. While every effort has been made to maintain consistency, users may find some differences in variable title and area of interest assignment.
Cohorts
- NLSY97
- Topical Guide to the Data
- Asterisk Tables
- I. Employment, Unemployment, and Job Search (age restrictions as of interview date)
- II. Schooling (age restrictions as of 12/31/96)
- III. Training (age restrictions as of interview date)
- IV. Income, Assets, and Program Participation
- V. Family Formation (age restrictions as of end of previous calendar year--12/31/96 in rd 1, 12/31/97 in rd 2, and so on)
- VI. Family Background (age restrictions as of 12/31/1996)
- VII. Expectations
- VIII. Attitudes, Behaviors, and Time Use
- IX. Health (age restrictions as of 12/31/96)
- X. Political Participation
- XI. Environmental Variables (in main data set)
- Education
- Employment
- Household, Geography & Contextual Variables
- Family Background
- Marital History, Childcare & Fertility
- Income
- Health
- Attitudes
- Crime & Substance Use
- Asterisk Tables
- Intro to the Sample
- Using & Understanding the Data
- Other Documentation
- Codebook Supplement
- Introduction to the NLSY97 Created Variable Appendices
- Appendix 1: Education Variable Creation
- Enrollment Status and Highest Grade/Degree - Appendix 1
- Date Received Diploma or Degree - Appendix 1
- Number of Grades Repeated or Skipped - Appendix 1
- Number of Schools Attended - Appendix 1
- Credits Earned toward Bachelor's/Associate's Degree - Appendix 1
- Date Left High School and Highest High School Grade - Appendix 1
- Private or Parochial School - Appendix 1
- SAT/ACT Scores - Appendix 1
- Training: Receipt of Certificate or Vocational License - Appendix 1
- Appendix 2: Employment Variable Creation
- Appendix 3: Family Background and Formation
- Household Size as of Survey Date - Appendix 3
- Marital Status and Marital/Cohabitation History - Appendix 3
- Fertility and Child Status - Appendix 3
- Number of Residences since Age 12 - Appendix 3
- Current Citizenship Status - Appendix 3
- Mother's Age at First Birth/Respondent's Birth
- Relationship to Household Parent Figures (Round 1 Parent Interview) - Appendix 3
- Relationship to Household Parent Figures (Rounds 7-9 Childhood Retrospective) - Appendix 3
- Relationship to Household Parent Figures (Interview Date) - Appendix 3
- Appendix 4: Geographic Variable Creation
- Appendix 5: Income and Assets Variable Creation
- Appendix 6: Event History Creation and Documentation
- Appendix 7: Continuous Month Scheme and Crosswalk
- Appendix 8: Instrument Rosters
- Appendix 9: Family Process and Adolescent Outcome Measures
- Appendix 10: CAT-ASVAB Scores
- Appendix 11: Collection of the Transcript Data (High School)
- Appendix 12: Post-Secondary Transcript Study
- Attachment 1: Census Industrial & Occupational Classification Codes
- Geocode Codebook Supplement
- Introduction to NLSY97 Geocode Data
- Attachment 100: Census Bureau State and County Codes
- Attachment 101: Metropolitan Statistical Area (MSA)/Core-Based Statistical Area (CBSA) Codes
- Attachment 102: IPEDS Data and College Identification Codes
- Attachment 103: Migration Distance Variables for Respondent Locations
- Attachment 104: Codebook Pages for Geocode and Zipcode Variables
- Questionnaires
- Errata
- Errata for NLSY97 Round 17 Release
- Errata for NLSY97 Round 16 Release
- Addendum: Additional NLSY97 Speech & Post-Secondary Variables Available
- Addendum: NLSY97 Post-Secondary Data and Transcript Data Files Now Available
- Errata for NLSY97 Round 15 Release
- Errata for NLSY97 Round 14 Release
- Errata for NLSY97 Round 13 Release
- Errata for NLSY97 Round 12 Release
- Errata for NLSY97 Round 11 Release
- Errata for NLSY97 Round 10 Release
- Errata for NLSY97 Round 9 Release
- Errata for NLSY97 Round 8 Release
- Errata for NLSY97 Round 7 Release
- Errata for NLSY97 Round 6 Release
- Errata for NLSY97 Round 5 Release
- Errata for NLSY97 Round 4 Release
- Errata for NLSY97 Round 3 Release
- Tutorials
- Technical Sampling Report
- Codebook Supplement
- Get Data
- Topical Guide to the Data
- NLSY79
- Topical Guide to the Data
- Asterisk Tables
- Education
- Employment
- Employment: An Introduction
- Work Experience
- Jobs & Employers
- Class of Worker
- Discrimination
- Fringe Benefits
- Industries
- Job Characteristics Index
- Job Satisfaction
- Job Search
- Labor Force Status
- Military
- Occupations
- Time & Tenure with Employers
- Wages
- Work History Data
- Employer History Roster
- Business Ownership
- Retirement
- Household, Geography & Contextual Variables
- Family Background
- Marital History, Childcare & Fertility
- Income
- Health
- Attitudes
- Crime & Substance Use
- Intro to the Sample
- Using & Understanding the Data
- Other Documentation
- Codebook Supplement
- NLSY79 Attachment 3: Industrial and Occupational Classification Codes
- NLSY79 Attachment 4: Fields of Study in College
- NLSY79 Attachment 5: Index of Labor Unions and Employee Associations
- NLSY79 Attachment 6: Other Kinds of Training Codes
- NLSY79 Attachment 7: Other Certificate Codes
- NLSY79 Attachment 8: Health Codes
- NLSY79 Attachment 100: Geographic Regions
- NLSY79 Attachment 101: Country Codes
- NLSY79 Attachment 102: Federal Information Processing Standards (FIPS)
- NLSY79 Attachment 103: Religion Codes
- NLSY79 Attachment 106: Profiles of American Youth (ASVAB Data/AFQT Scores)
- NLSY79 Appendix 1: Employment Status Recode Variables (1979-1998 and 2006)
- NLSY79 Appendix 2: Total Net Family Income Variable Creation (1979-2014)
- NLSY79 Appendix 3: Job Satisfaction Measures
- NLSY79 Appendix 4: Job Characteristics Index 1979-1982
- NLSY79 Appendix 5: Supplemental Fertility and Relationship Variables
- NLSY79 Appendix 6: Urban-Rural and SMSA-Central City Variables
- NLSY79 Appendix 7: Unemployment Rate
- NLSY79 Appendix 8: Highest Grade Completed & Enrollment Status Variable Creation
- NLSY79 Appendix 9: Linking Employers Through Survey Years
- NLSY79 Appendix 11: Round 12 (1990) Survey Administration Methods
- NLSY79 Appendix 12: Most Important Job Learning Activities (1993-94)
- NLSY79 Appendix 13: Intro to CAPI Questionnaires and Codebooks
- NLSY79 Appendix 14: Instrument Rosters
- NLSY79 Appendix 15: Recipiency Event Histories
- NLSY79 Appendix 16: 1994 Recall Experiment
- NLSY79 Appendix 17: Interviewer Characteristics Data
- NLSY79 Appendix 18: Work History Data
- NLSY79 Appendix 19: SF-12 Health Scale Scoring
- NLSY79 Appendix 20: Round 20 (2002) Early Bird and Income Recall Experiments
- NLSY79 Appendix 21: Attitudinal Scales
- NLSY79 Appendix 22: Migration Distance Variables for Respondent Locations
- NLSY79 Appendix 23: Revised Asset and Debt Variables and Computed Net Worth Variables
- NLSY79 Appendix 24: Reanalysis of the 1980 AFQT Data from the NLSY79
- NLSY79 Appendix 25: Center for Epidemiologic Studies Depression (CES-D) Scale
- NLSY79 Appendix 26: Non-Response to Financial Questions and Entry Points
- NLSY79 Appendix 27: IRT Item Parameter Estimates, Scores and Standard Errors
- NLSY79 Appendix 28: NLSY79 Employer History Roster
- Geocode Codebook Supplement
- Appendix 7: Unemployment Rates
- Appendix 10: Geocode Documentation
- Attachment 100: Geographic Regions
- Attachment 101: Country Codes
- Attachment 102: State FIPS Codes
- Attachment 104, Part A: 1981 Standard Metropolitan Statistical Areas (SMSAs)
- Attachment 104, Part B: 1983 Metropolitan Statistical Areas (MSAs)
- Attachment 104, Part C: 1983 Consolidated MSAs and Associated Primary MSAs (CMSAs and PMSAs)
- Attachment 104, Part D: 1983 PMSAs and Associated CMSAs
- Attachment 104, Part E: 1988 MSAs, CMSAs, and Associated PMSAs
- Attachment 104, Part F: 2004 MSAs, CMSAs, and Associated PMSAs
- Attachment 104, Part G: 2006 Core-Based Statistical Areas (CBSAs)
- Attachment 105: Addendum to FICE Codes
- Attachment 106: Codebook Pages for Geocode and Zipcode Variables
- Questionnaires
- Tutorials
- Errata
- Technical Sampling Report
- School & Transcript Surveys Documentation
- Codebook Supplement
- Get Data
- Topical Guide to the Data
- NLSY79 Child/YA
- Topical Guide to the Data
- Intro to the Sample
- Using & Understanding the Data
- Other Documentation
- Codebook Supplement
- Appendix A: HOME-SF Scales (NLSY79 Child)
- Appendix B: Composition of the Temperament Scales (NLSY79 Child)
- Appendix C: Motor & Social Development (NLSY79 Child)
- Appendix D: Behavior Problems Index (NLSY79 Child)
- Appendix D, Part 1: Composition of the BPI subscales
- Appendix D, Part 2a: BPI Anxious/Depressed Subscale
- Appendix D, Part 2b: BPI Antisocial Subscale
- Appendix D, Part 2c: BPI Dependent Subscale
- Appendix D, Part 2d: BPI Headstrong Subscale
- Appendix D, Part 2e: BPI Hyperactive Subscale
- Appendix D, Part 2f: BPI Peer Conflicts/Withdrawn Subscale
- Appendix D, Part 2g: BPI Full Scale
- Appendix D, Part 3a: BPI Internalizing Subscale
- Appendix D, Part 3b: BPI Externalizing Subscale
- Appendix D, Part 3c: BPI Total Scores
- Appendix E: Sample SPSSx Program for Merging NLSY79 Child/YA & Mother Files
- Appendix F: Sample SAS Program for Merging NLSY79 Child/YA & Mother Files
- Appendix G: NLSY79 Child Assessment Scores, Reference Numbers (2010-2014)
- Appendix H: Identification Codes in the Child and Young Adult Database
- Attachment 100: Codebook Pages for Young Adult Geocode Data
- Questionnaires
- Errata
- Errata for 2014 Child/Young Adult Release
- Data Addition: New Work and School Status Variables Created
- Errata for 2012 Child/Young Adult Release
- Errata for 2010 Child/Young Adult Release
- Errata for 2008 Child/Young Adult Release
- Errata for 2006 Child/Young Adult Release
- Errata for 2004 Child/Young Adult Release
- Errata for 2002 Child/Young Adult Release
- Errata for 2000 Child/Young Adult Release
- Errata for NLSY79 Child Interview Dates 1986-1992
- Research/Technical Reports
- Codebook Supplement
- Get Data
- NLS Mature and Young Women
- NLS Older and Young Men