NLSY79 Child and Young Adult

The panel dimension of the NLSY79 data collection permits one to cumulate sample cases for children at specified ages across survey points, thus attaining rather substantial sample sizes for those ages. Pooling in this manner also can greatly enhance the heterogeneity of the sample for specific research topics. The trade-off to this methodology is that the ability to follow a particular age cohort across survey years becomes somewhat limited, although it is still doable for selected research topics. Table 1 below highlights potential sample sizes using this approach.

Pooling the Child samples. From the perspective of the younger children, it is possible to attain single year of age samples numbering in the thousands for specific research efforts. For example, if one wishes to examine associations between scores on the digit span assessment and other factors for seven year olds, it would be possible to cumulate a sample of about 4,000 seven-year-old children from the first to the current assessment survey year (see Table 1 below). Because these children would have been born to mothers in all years between 1979 and the current survey round (see Table 2 in the Sample Design section), the mothers of these children would range in age from their teens to their forties. The relevance of this pooling approach for evaluation of the child data, utilizing various assessments, is dealt with in the "Repeat Assessments" section of the Child Assessments--Introduction.

Pooling the Young Adults. Parallel estimates can be found for young adults. Because the young adult interviews have only been ongoing since the 1994 survey round, no single year-of-age cumulative estimate can include more than eleven points. Nonetheless, returning to Table 1 below, the number of cases cumulated in this way for ages 15 to 18 all attain single year of age totals of between 3,417 and 3,560 cases. It is worth noting that this sample cumulation modestly increases the heterogeneity of these young adult samples. For example, cumulating cases at these early young adult ages expands the age of the mothers at children's birth from mid-adolescence to the late forties. Because beginning in 2010 young adults age 31-32, 35-36, 39-40, 43-44, etc., as of December 31 of the survey year are not fielded, pooled sample sizes in these age ranges will be constrained.

These sections outline some research topics for which the NLSY79 Child and Young Adult data are particularly appropriate. Specific topics are not explored in depth but instead are presented as examples of a range of subjects that can be investigated. The focus here is on ways in which data from the main NLSY79 mothers, the younger children, and the young adults can be linked, allowing researchers to carry out not only within but also cross-generational research. Specific procedures for accessing and linking the various data files are discussed in Linking Children, Young Adults, and Mothers.

Note: Throughout these sections, the "current survey round" refers to the most recent public data release.

The NLSY79 main respondents were first interviewed in 1979.  An in-depth discussion of the information available for these main respondents is presented in the most recent NLSY79 User's Guide. As of the current survey round, the NLSY79 Child/Young Adult sample encompasses nearly all of the children that will ever be born to this cohort of women -- women who were 55-64 years old as of their 2020 interview date -- and they range in age from infancy into their late-forties. Large samples of these children are available for analysis throughout childhood and adolescence. Further, because growing numbers of children enter the young adult ages with each survey round, researchers are able to undertake analyses relating to transitions into adulthood for increasingly representative samples of youth. In addition, large minority samples are available, and as described in the sections of this guide on the sample, a variety of sibling-oriented analyses are possible. By pooling groups of children at certain ages across a number of years, researchers can also enhance sample sizes for relatively narrow age ranges, while at the same time improving the heterogeneity of the sample.

Further, a revised custom weight program is now available that permits users to more effectively combine weighted samples across survey years. Users do need to keep in mind that the oldest children were born to young NLSY79 mothers (and that the youngest children in the current survey round were born to mothers at the oldest ages). However, this sample selection issue has become less significant over time, as with every passing survey round the older children are increasingly born to women who gave birth at mainstream childbearing ages. See the "Sample Changes over Time" paragraphs in the Sample Design section for more detailed information about maternal age at birth.

Click a topic below for more information:

In addition to this online User's Guide, a number of documentation items are provided to help users understand the Child and Young Adult data. Except for the Codebook, which is accessed through the NLS Investigator search and extraction Web program, all of these items are available within the Child section of this website. Additional assistance is available through NLS User Services.

Codebook

The NLSY79 Child and Young Adult (and main Youth) data files are each documented by a codebook that lists each variable and briefly describes its content. Each variable has a codebook page that contains the variable's unique reference number, coding categories for the variable, frequency distributions, minimum and maximum values, and any special notes. Entries for questionnaire items also contain links to the previous and next question in the instrument. The hyperlinked reference numbers that appear in codebook entries for created variables simply take the user to the next item in the list, generally within the area of interest. Users can review codebook pages for variables of interest through NLS Investigator, and extracts of variables include a custom codebook file containing codebook pages for all variables in the extract. For more information, see the Investigator User Guide.

Child and Young Adult survey instruments

Since most of the constructed variables and test scores found within the Child data set are derived directly from one or more survey instruments, users should have access to at least one set of questionnaires. Copies of the Child and Young Adult questionnaires and interview aids are available in either PDF or HTML format on the Questionnaires page. This page has links to the following questionnaires:

• Child Supplement (CS): public user version of the Child Supplement questionnaire (paper and CAPI); contains the interviewer-administered assessments
• Child Self-Administered Supplement (CSAS): public user version of the self-report questionnaire for children age 10-14; administered on paper, PDA or laptop
• Mother Supplement (MS): public user version of the maternal report questionnaire for each child; contains the mother-report assessments
• Young Adult Questionnaire: public user version of the Young Adult CAPI questionnaire
• Child School Survey Principal Questionnaire: paper questionnaire about school characteristics completed by school principal for each child in the 1995-1996 NLSY79 Child School Survey
• Child School Survey Schooling Questionnaire: paper questionnaire completed by school personnel about each child in the 1995-1996 NLSY79 Child School Survey

NLS bibliographies

NLS User Services maintains an annotated, searchable archive of NLS research available by clicking the tab in the main menu. Records of more than 9,000 journal articles, working papers, monographs, reports, presentations, theses, and dissertations are available for users to search, retrieve, and print customized listings of NLS research. CHRR periodically compiles listings of research based on the NLSY79 child data. Some of these bibliographies are listed under Child Survey Resources on the Research/Technical Reports page.

Other documentation

In addition to the codebooks, variable descriptions, search indices, and items described above, CHRR provides the following materials to users as additional documentation for the NLSY79 Child and Young Adult data:

• NLSY79 Child Handbooks 1986-1992 (detailed information about the NLSY79 Child assessments and supplementary information about sample constraints in previous survey rounds)
• Child Assessment Tables reports (tabular summaries of assessment scores for survey rounds from 1994 to the present)

These handbooks and assessment tables reports are available on the Research/Technical Reports page.

Important information and errata

Periodically CHRR provides users with updates to the existing data or documentation. Notes are sometimes prepared that clarify certain elements of the current files. This information is compiled into a list of Errata posted to the Child/YA User's Guide. Updates to previous data rounds are noted in the documentation for those rounds. Users are strongly encouraged to consult the errata page as they are working on their research projects to ensure that they are aware of any notices that may affect variables of interest.

The Child/Young Adult data files contain many constructed variables drawn from multiple sources, including both cross-sectional and longitudinal information in both the child and mother records. Users of the Child/Young Adult data who wish to construct variables not found in the Child/Young Adult files may access the mothers' records in the main Youth files in order to obtain the necessary inputs. A useful variable for linking the mother's longitudinal record to the child is C00052.00, which defines the first survey year (of the mother) following the child's date of birth. The question name for this variable is FSTYRAFT. (NOTE: Children born prior to the 1979 survey date are assigned 1979 as their first post-birth survey point.)

In general, a researcher interested in creating a variable that references a particular post-birth survey point for all children would need to follow a two-step procedure. For example, to create a variable that defines the first post-birth survey maternal school enrollment status for all children from information collected at the mother's survey dates, one would take the following steps:

1. Find Question Name = FSTYRAFT (reference # C00052.00) to define the appropriate survey year following the child's date of birth
2. Use the value for FSTYRAFT to choose a maternal enrollment status variable, depending on the date of the birth of the child

If the child's first post-birth survey year FSTYRAFT is 1982, the maternal enrollment status variable as of the 1982 interview (Qname = ATTSCH1982, reference # C00570.00) would be selected. Similarly the appropriate enrollment status information could be combined across the relevant surveys into one created "first post-birth survey enrollment status" variable.

For more refined linking procedures, the user may need to access maternal interview dates as well as the dates of many relevant events, such as school leaving, job changes, and marital changes. Variables that are keyed to the child's date of birth or to the mother's date of interview can be used to (1) link social, economic, and demographic maternal behaviors with a child's birth or age at a particular point or to (2) define the survey point closest to a particular child's birth or attained age.

The pre- and postnatal variables (C03200.00-C03392.10) are already defined in an appropriate life cycle context, since they reference either the pregnancy leading up to a particular birth or an event/behavior during the first year following a birth. A missing value in this series of constructed child variables means that at least one input from the main Youth file was missing (refer to the note in the Child codebook for C02700.00).

Linking Data Files across Cohorts

The child identification code (CPUBID, C00001.00) allows the user to link children with their siblings on the NLSY79 Child files and with their mothers on the main NLSY79 files. The child ID is created by appending a 2-digit code (01 to 11) to the end of the mother's public ID (R00001.00 in the NLSY79 data). Thus, children with the same first 5 digits in their IDs are siblings. Since the child ID contains the first 5 digits of the mother ID, either the child ID or the mother ID (MPUBID, C00002.00) enables the users wishing to create a mother-based file to extract maternal characteristics and write them out only for mothers. Appendix H provides additional information about the identification codes available in the Child/YA data.

Child ID vs. Young Adult ID. Users will note that identification codes are provided for all children as CPUBID (C00001.00) in the CHILD BACKGROUND area of interest and again for young adults as CASEID (Y00001.00) in YA COMMON KEY VARIABLES. The only distinction between these two variables is that the young adult CASEID is only available for children who have been interviewed as young adults. The variable called CPUBID is a comprehensive ID code with values for all children (including young adults), regardless of age or interview status. The YA CASEID is included for the convenience of users accessing only the Young Adult data.

Linking Children and Young Adults to Mothers. Linking NLSY79 mothers to their children can be done by using the case identification code for both the mother (R00001. in the main youth file) and the child (C00001.00). To merge the files, save the Child and Young Adult case ID (C00001.00, CPUBID or the Young Adult case ID, Y00001.00, CASEID) and mother case ID (C00002.00, MPUBID) from an extract of the Child and Young Adult file and save the mother case ID (R00001.00) from an extract from the main NLSY79 file. The mother's case ID will be the same in both files. The CPUBID child ID is provided for all children, regardless of whether they are under age 15 or classified as young adults in any survey year. Appendix E (SPSS) and Appendix F (SAS) in the Codebook Supplement offer sample programs designed to assist users in merging files.

NLS Tutorial: Linking Mothers and Children. We have produced a tutorial that gives detailed instructions on how to link a data file of young adult children extracted from the Child/Young Adult database with a file from the main Youth file for mothers. This example with step-by-step instructions will assist users still uncertain about the linking process.

• Child
• Young Adult

Child

Interviewer Remarks in the Child Supplement. At the conclusion of each child interview, interviewers complete a summary evaluation of the overall interview and a series of "testing conditions" items, found at the end of the Child Supplement. These items, most of which are prefixed for with the phrase TESTING CONDITIONS or INT REMARKS, are assigned to the CHILD SUPPLEMENT area of interest. The following titles are used to describe these items in the documentation:

• INT REMARKS: ANY PROBLEMS WITH CHILD'S HEARING?
• INT REMARKS: ANY PROBLEMS WITH CHILD'S STATE OF HEALTH?
• INT REMARKS: ANY PROBLEMS WITH CHILD'S VISUAL SHARPNESS
• TESTING CONDITIONS: AMOUNT OF INTERFERENCE FROM DISTRACTIONS
• TESTING CONDITIONS: AMOUNT OF INTERFERENCE FROM INTERRUPTIONS
• TESTING CONDITIONS: AMOUNT OF INTERFERENCE FROM LIGHTING
• TESTING CONDITIONS: AMOUNT OF INTERFERENCE FROM NOISE
• TESTING CONDITIONS: AMOUNT OF INTERFERENCE FROM OTHER SOURCE
• TESTING CONDITIONS: AMOUNT OF INTERFERENCE FROM PRESENCE OF OTHERS
• TESTING CONDITIONS: AMOUNT OF INTERFERENCE FROM TEMPERATURE
• TESTING CONDITIONS: CHILD'S ATTITUDE TOWARD BEING TESTED
• TESTING CONDITIONS: CHILD'S COOPERATION
• TESTING CONDITIONS: CHILD'S MOTIVATION/INTEREST
• TESTING CONDITIONS: CHILD'S PERSEVERANCE/PERSISTENCE
• TESTING CONDITIONS: CHILD'S RAPPORT WITH INTERVIEWER
• TESTING CONDITIONS: WERE THERE ANY OTHER SOURCES OF INTERFERENCE?

The Child Supplement also contains two items in which the Interviewer indicates how shy the child was at the beginning and end of the interview. In 1986, these two items are documented as follows:

1. SHYNESS AT START
2. SHYNESS AT END

After 1986, the titles for these two items are as follows:

1. HOW SHY/ANXIOUS WAS CHILD WHEN HE/SHE MET INTERVIEWER
2. TESTING CONDITIONS: HOW SHY/ANXIOUS WAS CHILD AT END OF SUPPLEMENT?

In addition, the CHILD SUPPLEMENT area of interest contains interviewer check items that indicate the following:

• THIS HEALTH INFORMATION RELEVANT TO FUTURE INTERVIEWS?
• WHERE WAS CHILD SUPPLEMENT ADMINISTERED?
• IN WHAT LANGUAGE WAS THIS CHILD SUPPLEMENT ADMINISTERED?
• ANY SKIP ERRORS, QUESTIONS THAT WERE CONFUSING OR DIDN'T WORK?

Assessment-Specific Interviewer Remarks. At the conclusion of each interviewer-administered assessment in the Child Supplement, there is a series of interviewer remarks designed to describe the factors that might influence a child's performance. For each assessment the interview records:

• the child's energy level
• who else was present during testing
• what impact others might have had on a child's performance
• whether an assessment was prematurely terminated

Interviewers are also instructed to make comments in the assessments or interviewer remarks section if other languages were used in the interview to facilitate understanding. These remarks are in the CHILD SUPPLEMENT area of interest. The titles for these items are prefixed with the name of each assessment.

CSAS Interviewer Remarks. In the paper years, the Interviewer was asked to complete this question after the child had completed the Child Self-Administered Supplement:

• LIST QUESTIONS THAT CONFUSED, ANGERED, OR CAUSED DISCOMFORT TO THE CHILD OR QUESTIONS THAT YOU FEEL THE CHILD DID NOT ANSWER TRUTHFULLY. EXPLAIN.

Starting in 2002, when the Child Self-Administered Supplement became a CAPI instrument, the CSAS interviewer remarks question is documented as followed:

• CHILD SELF-ADMIN: INT REMARKS-NO QUESTION CONFUSED OR ANGERED CHILD

Starting in 2006, an additional question was added:

• CHILD SELF-ADMIN: INT REMARKS - CHILD HAD PROBLEMS WITH HOW TO USE DEVICE (LAPTOP)

Interviewer Remarks in the Mother Supplement. In the Mother Supplement CASI section, the interviewer indicates the language of administration, which, if any, questions caused problems and rates the mother's attitude about using the CASI section. These items are documented as follows:

• MS INTERVIEWER REMARKS: IN WHAT LANGUAGE WAS THIS MS ADMINISTERED
• MS INTERVIEWER REMARKS: RATING OF RESPONDENT'S UNDERSTANDING OF QUESTIONS
• MS INTERVIEWER REMARKS: NO QUESTIONS CONFUSED, ANGERED RESPONDENT

To date, little in-depth analysis has been completed that uses the interviewer reports of testing conditions. One study based on the NLSY79 child data found that differences in achievement test scores by race/ethnicity could be partly explained by testing conditions, including interviewer characteristics, interviewer-child interactions, and the testing environment (Kim et al., 2003). In a study of intergenerational predictors of racial differences in achievement, Mandara, Greene and Varner used the testing evaluation items to construct a scale of "test-taking motivation." They found that motivation was one important predictor of achievement as measured by PIAT Math and Reading scores (Mandara, et al, 2006).

The NLSY Children 1992: Description and Evaluation (available on the Research/Technical Reports page) contains a discussion of the impact of testing conditions on selected outcomes. Analyses of the information about the presence of others during the testing indicate that younger children may experience some difficulty in certain cognitive tasks when there is interference in the testing environment and when other adults are present. Younger children who took the SPPC assessment tended to report more positive self-evaluation in the presence of other adults while the presence of other children tends to boost the reports of older children on this assessment. These early results helped inform the field-testing protocol so that interviewer procedures could be refined to minimize any external effects on child performance.

Young Adult

At the conclusion of each young adult interview, interviewers complete a summary evaluation of the overall interview. The Young Adult interviewer remarks section, located at the end of the questionnaire, contains interview-specific and interviewer comment information, including the type of interview (personal or telephone); the language used to conduct the interview; various interviewer remarks on respondent's race, attitude, understanding of the questions, and presence of anyone else during the interview; and interviewer identification codes. These variables are located in the "YA Interview Remarks" area of interest and have question names starting with "QIR."

Appropriate sample weights are available in each year to adjust the un-weighted sample cases for the minority oversamples and year-to-year sample attrition. The sample weights for younger children and young adults:

1. adjust the un-weighted data for sample attrition of mothers and their children since the first survey round (1979) and the sample reduction due to the loss of the military and economically disadvantaged white oversample and
2. adjust the sample for the over-representation of black and Hispanic youth. 

For those interested in generating population estimates for prior survey rounds, sample weights for those survey rounds are available. 

Using these weights translates the un-weighted sample of children into a population that represents all children who have been born by that date to a nationally representative sample of women who were 14 to 21 on December 31, 1978. Beginning in 2002, a revised algorithm was used to compute the sample weights. For the 1986-2000 survey years, two sample weight variables are available for each year: the originally released sample weight and a revised weight using the new algorithm.

Weights are computed only for younger children who have been interviewed or young adults who have been fielded and interviewed in a given year. Children not assessed and young adults not interviewed (or interviewed but not fielded) in a given year are assigned a weight of zero for that year. Table 1 lists the complete set of child, young adult, and mother sample weights.

Revised Sampling Weights. Starting with the 2002 child survey round, an updated automated computation procedure was instituted to allow users to create custom sets of weights for analyses that require more than cross-sectional weighting information. The automated process was designed both to sum the same population totals and to follow the same procedures as done previously. Because of slight differences in the results, an additional set of revised cross-sectional weighting variables is provided for the Child survey years 1986-2000 (CSAMWTyyyy_REV) and for Young Adult survey years 1994-2000 (YAyyWEIGHT_REVISED). Users should find minimal differences between the two series of sample weights but are strongly encouraged to check if switching between the two types of weights affects their results.

The child/young adult sample weights adjust for sample attrition of NLSY79 mothers and children (including the loss of the military and white oversamples) and for over-representation of black and Hispanic respondents. Each set of cross-sectional child sample weights is computed by multiplying the mother's 1979 sample weight by a factor that is the reciprocal of the rate at which children in particular age/sample-type/sex cells are assessed or interviewed. 

The current public release contains a complete set of custom child weights for all child survey years in which values are assigned according to the following criteria:

• Each non-interviewed child's weight = 0.
• Each interviewed child's weight is equal to the mother's weight multiplied by the number of children her interviewed child represents.
• Every interviewed child represents himself or herself plus the number of non-interviewed, known children, plus the number of children estimated to have been born to non-interviewed mothers. This last set of imputed children is determined by determining the number of years since the mother was last interviewed and assigning the same number and ages of children born based on what was reported for interviewed mothers of the same sex and race.

In the other NLS cohorts, the cell collapsing code is relatively complex and allows the program to merge almost any set of adjacent cells. In creating the weights for the Child-Young Adult cohort the cell collapsing code is simpler. Generally cells are collapsed as follows:

• Only the end points are collapsed (oldest and youngest kids)
• The end point is the same for males and females (to follow how it is done prior to the custom weighting program)
• Cells are collapsed if there are fewer than 10 observed children

Customized Longitudinal Weights. Researchers who need to weight individuals who participated in multiple survey rounds (i.e., such as all children who participated in 1988-2008) are referred to the custom weighting program. Caution should be used when comparing weighted estimates across years since the composition of the sample can change in subtle ways depending on who was interviewed. The custom weighting program also offers the option of getting weights for a specific set of respondent ids.

Sample Weights to Identify Interviews. Users can also employ the Child sample weight variables to delineate their analysis sample and to identify respondents interviewed in each survey round. Restricting the sample to those cases with a sample weight value greater than zero "0" will yield the set of respondents interviewed and/or assessed in a particular survey year. A child sample weight (CSAMWTyyyy_REV or CSAMWTyyyy) GT "0" will indicate the number of children with either a Mother Supplement and/or Child Supplement.

Please note that in 2000, four Young Adult respondents who were part of the pool of oversample cases that were not fielded were inadvertently interviewed. For these four respondents, their interview data are included in the public release, but their sampling weights are set to zero. Similarly, since 2010, in each survey round some Young Adults over thirty who were not fielded ended up being interviewed. For these respondents, their interview data are included in the public release, but their sampling weights are set to zero. More detail on sample weights and interview status can be found in the section Missing Data: Noninterviews and Item Nonresponse.

Where to Find the Sample Weights. The list of sample weight variables for children and young adults appears in Table 1 above.

The Child sample weights are assigned to both the SAMPLING WEIGHTS and the yearly ASSESSMENT areas of interest. Children who have been assessed or interviewed in a given year have values greater than 0 on their sample weight for that year.

The Young Adult sample weights for each year are assigned to both the SAMPLING WEIGHTS and the YA COMMON KEYVARS areas of interest. These YA sample weight variables are specific to young adults interviewed in that year so that any young adult not interviewed or any child who is not a young adult in that year is assigned a value of "0." The Young Adult sample weights are assigned to both the SAMPLING WEIGHTS and the YA COMMON KEY VARIABLES areas of interest.

A Note about Sampling Weights

NLSY79 Child and Young Adult 1994-2016 data set includes revisions to several Young Adult sampling weights as well as the replacement of two revised Child sampling weights.

Young Adult Sampling Weights. Beginning in 2010, young adults over age 30 are only interviewed every four years. The interviewed sample is selected by age as of December 31 of the survey year, so that approximately half of the older young adults are eligible each round. Since 2010, young adults age 31-32, 35-36, 39-40, 43-44, etc. as of December 31 of the target year have not been fielded.

The algorithm creating the round-specific sampling weights did not adequately account for this change in fielding, leading older YAs in the age groups that were fielded (33-34, 37-38, 41-42, etc.) to receive disproportionately high weights. The algorithm has been readjusted and the round-specific sampling weights for the interviewed YAs over age 30 have been replaced in the following variables:

Y26159.00    [YA10WEIGHT]
Y29663.00    [YA12WEIGHT]
Y33318.00    [YA14WEIGHT]

Child Sampling Weights. An error in the code creating the revised round-specific sampling weights that were released in 2002 led to the 1986 and 1988 Child Sampling weights to be incorrectly calculated. The following weights have been replaced for all affected children:

C05812.01    [CSAMWT1986_REV]
C08007.01    [CSAMWT1988_REV]

The NLSY79 Child and Young Adult data release contains comprehensive information from the 1986 through the current survey round. The file also contains child-specific information from the mother's main Youth interviews. Certain variables are derived from the mother's longitudinal record while other data items represent the questions administered during the Child and Young Adult interviews and the responses from each child assessment. Finally, there is an extensive set of created variables on the file, based on the assessment and interview data.

Detailed information on the types of data available for the NLSY79 Children and Young Adults can be found by examining the field instruments and by searching the database indices. Instructions on how to search the database can be found in the Investigator User Guide. Researchers who are interested in items based on data from the mother's record are encouraged to access copies of the main Youth questionnaires and to review the NLSY79 main Youth documentation. These items are available in the NLSY79 section of the website. Information on how to link child and mother data can be found primarily in the section on Linking Children, Young Adults, and Mothers.

The NLSY79 Child data include demographic and family background, pre- and postnatal health history, home environment reports, information on child care and school experiences, items and scores from the biennial child assessments, and reports from the child "10 and older" self-report questionnaire. The Young Adult contains questionnaire items from all Young Adult interview years, covering areas such as family background, schooling, training, work and military experiences, relationship history, fertility, health, and drug and alcohol use, as well as a set of created variables for each round. Geographic information for young adults is available on a separate geocode file.

The type of variable may affect (1) the physical placement of the variable within the codebook (its sequence in the reference number list) and (2) the assignment of a variable to a particular area (or areas) of interest. Types of variables that appear in the public releases of the Child and Young Adult files include:

1. Direct (or raw) responses from a questionnaire or assessment or other survey instrument.
2. Recoded or edited variables constructed from raw data according to consistent procedures, e.g., coding of verbatim responses about jobs done for pay or religion other than the precoded categories. Such variables are marked as recode versions of the original.
3. Constructed variables based on responses to more than one data item or multiple reports to the same item, either from cross-sectional or longitudinal information. Some of these created variables are indices or scale summations, such as the assessment scores, and others are individual items edited for consistency where necessary, e.g., child background characteristics such as age, date of birth, and gender. (See additional information below.)
4. Constructed variables from a non-NLS data source, e.g., the County & City Data Book information present on the NLSY79 Young Adult geocode file.
5. Variables provided by NORC or another outside organization based on sources not directly available to the user, e.g., the transcript data and test scores from the child school survey.
6. Data collected from or about one universe of respondents reconstructed with a second universe as the unit of observation, e.g., variables on the NLSY79 Child data file that are based on inputs from the mother's main Youth record but linked to each child.

Constructed Child variables based on main Youth data. Constructed variables, drawn from the mothers' records, provide information on each mother's household composition, quarterly employment referenced to the birth of each child, and family background. While most information is cross-sectional, many variables link maternal events or behaviors to the child's life cycle-specific points after, or in some instances, before the child's birth. Any item from the complete record of the mother's main Youth record can be linked to the Child and Young Adult files.

Constructed Child- and Mother-Specific Variables. In addition to the questionnaire items and constructed assessment scores the NLSY79 Child data set contains a number of other constructed variables. Some constructed variables, such as pre- and postnatal care and child usual residence, are drawn from child-specific information collected in the mother's main Youth interview. Other constructed items, such as maternal household composition and family background, are created from mother-based information that does not vary across children. Constructed variables are generally found in the following Areas of Interest:

• CHILD BACKGROUND
• CHILD CARE
• FAMILY BACKGROUND
• MATERNAL HOUSEHOLD COMPOSITION
• PRE/POST NATAL CARE

These created items include sibling identifiers, maternal family background, maternal household composition at each interview, and family educational background. Details on these constructed variables can be found in the Topical Guide to the Data. Mother-specific information present on the NLSY79 main data file and on special data sources such as the work history and geocode main Youth files can be linked with the Child data by case ID.

Constructed Young Adult Variables. In addition to the questionnaire items from the Young Adult surveys, several constructed variables for Young Adults are available. Some of these created variables are available for all young adult respondents who were interviewed in any survey year (designated as XRND), while others are specific to a particular survey round. The Young Adult constructed variables are located in the Area of Interests called YA COMMON KEY VARIABLES and YA FERTILITY AND RELATIONSHIP DATA - CREATED. 

The following key variables are constructed for all young adults: young adult ID (Y00001.00, CASEID), date of birth, gender, race, the ID code of the mother, comprehensive biological child information, dates of first marriage and first cohabitation, as well as the following:

Additionally, XRND flags for completing specific degrees, as well as the month and year the degrees were received, are available for all young adults.

Details about key variables: Two key identification codes are provided: that of the Young Adult and that of the mother. Any child who has not yet aged into the Young Adult sample, or who is ineligible for fielding, or who has been fielded but not interviewed, will have a missing value (-7) on these two ID variables. Only children who have ever been interviewed as Young Adults have valid values. These variables are provided for users who want to quickly restrict their sample to ever-interviewed Young Adults. The ever-interviewed Young Adults also have an updated date of birth (month and year), gender, and race based on mother's racial/ethnic cohort from the 1978 screener.

Beginning with the 2000 release, three interview status variables are provided. First is the year of most recent Young Adult survey (Y12051.). This variable allows users to quickly identify when data for a non-year-specific variable would have been pulled. For example, if a respondent was last interviewed in 1994, only information from that year would have been available to use in constructing variables such as ever cohabited or ever reported a first marriage. 

The second interview status variable is the number of Young Adult interviews completed by a respondent (Y12052.). This variable allows users to assess how many respondents have multiple time points for repeated measures. Users are reminded, however, that there are a variety of factors that influence a respondent's value on this variable, such as when the respondent aged into the sample, during what years there were age or other restrictions applied to the fielded sample, and whether or not the respondent was actually interviewed in a given year. There are two flags per survey year, located in the CHILD BACKGROUND area of interest, allowing the user to identify whether a respondent was eligible to be interviewed as a Young Adult and whether or not a Young Adult interview occurred.

The last of these interview status variables is the number of Child survey years where the respondent has at least some interview or assessment data available (Y12053.). Users should be aware that the Child survey consists of two or three instruments, depending on the age of the child, and some respondents may have data for only one of these instruments in a given survey year. This variable, as with the number of Young Adult interviews, is provided to help users gain a quick portrait of data availability. 

New Variables Created by Researchers. Researchers sometimes use the NLS public datasets to generate a new variable to use in their research. In some cases, researchers like to make that new variable publicly available (through their own data repository) so that it can be easily accessed for follow-up studies. This is permissible as long as researchers are using public NLS data (rather than restricted) and that they make it clear they are the author of the variable rather than the NLS team.

Each NLSY79 child variable has a "question name" that helps to identify it in the data file and permits users to locate the original question in the questionnaire. Variables in the NLSY79 child data are generally named according to the source from which they are derived. Items from the Child, Mother, and Child Self-Administered supplements have question names linked to the location in the instrument. For example, "CS94-14" (HAS CHILD EVER BEEN ENROLLED IN HEAD START?) comes from Q.14 asked in the first section of the Child Supplement in 1994. Acronyms are used to identify the scores derived from the child assessments administered at the time of the survey (e.g., BPI2002 for Behavior Problems Index-Raw Score, 2002). Mnemonic names identify constructed variables that are based on inputs taken from the main NLSY79 survey (e.g., AGEMOM2006 for Age of mother at interview date, 2006).

Through 1998, questions from the mother and child instruments are generally identified by "MS" for Mother Supplement or "CS" for Child Supplement and, starting in 2000, "CSAS" for the Child Self-Administered Supplement. The two digits that immediately follow this prefix refer to the year of the survey. Starting in 2000, question names for items from the child questionnaires generally indicate the topical section of the instrument from which each question was derived. For example, child question names beginning with "SCHL" come from the schooling section of the Child Supplement questionnaire; items prefixed with "HLTH" designate the child health questions in the supplement. The question name also indicates the order in which the question was administered within each section of a questionnaire. 

Constructed variables are usually named according to the topic of their content. The item called "FSTYRAFT" (C00052.00) in the CHILD BACKGROUND area of interest refers to the "first survey year of mother after the child's birth." Such items on NLSY79 mothers and their children are usually based on multiple inputs from the main youth and child survey instruments. Codebook entries for these items may include a reference to one or more main file reference number to give the user an example of the main Youth question on which the child-specific item is based. For example, in the PRE/POST NATAL CARE area of interest, the item PRE0009 (C03201.00) refers the user to R13284.00 in order to see the inputs to the variable that were extracted from the main Youth file.

• Child Question Naming Conventions
• Young Adult Question & Variable Names
• Child & Young Adult Reference Numbers

Child Question Naming Conventions

Mother Supplement Question Names

From 1986-1996 question names for items in the Mother Supplement have the following three components: (1) "MS" to designate the source of the item, (2) a 2-digit number to indicate the year of the survey round, and (3) deck and column number, used to designate the physical location on a data punch card in the days of paper data input. For example, in the item listed below, MS960329, the "MS" indicates the Mother Supplement, the "92" means the item is from the 1992 survey, and "0329" shows that the item was in Deck 3, Column 29 in the booklet.

In 1998 a similar system was used in naming Mother Supplement questions except that section number and question numbers replace the deck and column numbers, which were no longer relevant. In the example below, MS981B01 means that this item is from the Mother Supplement, 1998, Section 1-B (the HOME), question 1.

In 2000 a new naming system was introduced that more closely parallels the conventions used for the main Youth and Young Adult surveys. As seen in the example below, questions from the Mother Supplement still use the MS designation as well as a reference to the section and item number within the section, but the question names do not indicate the year of the survey.

NOTE: In 2000 the HOME and Temperament items have different question naming conventions depending on the age of the child. Items for children under age 4 that were administered in the Child Supplement are named according to the name of the assessment (e.g., HOME-B01 above). HOME and Temperament questions for children age 4 and older appear in the Mother Supplement and are therefore prefixed with "MS" followed by the section and item number (MS1-A01 means Mother Supplement, Section 1-A, question 01). Notes have been entered into the codebook for these items to alert users to this change in 2000. In 2002, all these mother-report assessment items returned to the Mother Supplement, where they continue to be administered.

Question Names for the MS in the main Youth Questionnaire. Starting in 2006, to reduce the time burden on mothers, the Mother Supplement was fully integrated into the mother's main interview as part of the Fertility Section of the Youth questionnaire. The content and basic structure of the child-based Mother Supplement were preserved, but instead of administering separate questionnaires, one for each child, interviewers asked the Mother Supplement questions in a series of child-by-child "loops" as part of the mother's main interview. The Mother Supplement data items appear both in the main Youth file and as child-based items in the MOTHER SUPPLEMENT2006-current survey areas of interest in the Child file. While the Mother Supplement question names in the mother's main Youth documentation contain the same string used for those questions in recent years, Mother Supplement items in the Child file are now all prefixed with "MS."

For example, the item on Head Start enrollment for Child 01 and Child 02 in the mother's main Youth questionnaire is documented as follows in the mother's main Youth data record:

The child-based version of this same Mother Supplement variable is labeled as follows in the Child file:

NOTE: In general, users of the Child data should access the "child-based" version of the Mother Supplement. Users of the Head Start data may be interested to know that mothers too were asked in 1994 if they attended Head Start.

Child Supplement (CS) Question Names

Through 1992, question names for items administered in the Child Supplement are constructed as follows: (1) "CS" to designate the Child Supplement, (2) a 2-digit number to indicate the year of the survey round, and (3) deck and column number, used to designate the physical location on a data punch card used in the early survey rounds. When CAPI was introduced in 1994, questions were no longer identified by deck and column but simply by item number.

Starting in 2000, questions in the Child CAPI Supplement are generally identified by the section of the questionnaire. In the example that follows, BKGN stands for the Child Background section of the questionnaire:

NOTE: Starting in 2006, nearly all the child background questions were moved into the Mother Supplement, which was integrated into the mother's main Youth interview. So an item such as BKGN-12, now appears prefixed as "MS-BKGN-12."

Child Self-Administered Supplement (CSAS) Question Names

Questions in the Child Self-Administered Supplement for children 10 and older are prefixed by "CS" until the 2000 survey when they begin with "CSAS." Through 1996, deck and column numbers were used to designate the question location in the CSAS booklet. The following example designates the year "96" and then deck "01", column "13" (pg. 3 of the paper booklet):

In 1998, item numbers are used.

Starting in 2000, the prefix CSAS designates that the item is from the Child Self-Administered Supplement and the item number corresponds to the actual question in the instrument:

Young Adult Question & Variable Names

Question names in the Young Adult surveys follow one of three general patterns. Individual items from the Young Adult CAPI questionnaire are usually prefixed by "Q" and the section number. The suffix generally indicates the order in which questions appear. Because questions asked in multiple rounds retain the same question name, many suffixes also include letters (e.g., Q4-31B). Thus, Q2-19 represents the following question (asked in each survey year) of the Family Background portion (Section 2) of the YA CAPI questionnaire:

In prior releases, questions from the Young Adult self-report booklet in 1994 and 1996 were prefixed with "YA" followed by the survey year, and then a designation of the deck and column number. In 1998, question names for these self-report items no longer incorporated the deck and column numbers and were simply named according to question number sequence in the booklet.

Since 2000, when the self-report questions were first incorporated into the self-report section of the YA CAPI questionnaire, they have been prefixed by "YASR":

In order to make the Self-Report data easier to search in Investigator, for the 2018 release, the questions from the YA Self-Report Booklets for 1994 to 1998 have been renamed to follow the naming conventions used since 2000. Any question that was in the YASRB and has remained in the CAPI questionnaire will now have the same question name across all rounds in which it was asked. Similarly, those questions only asked in the YASRB will have a CAPI-style name that allows users to easily identify these questions across the rounds in which they were asked.

Constructed variables on the Young Adult file are identified by mnemonic names related to their content. For example, the series of variables that identifies the type of residence in each survey round are named "RESTYPE" followed by a year designation.

Child & Young Adult Reference Numbers

All variables on the NLSY79 Child and Young Adult files are assigned unique identifiers called reference numbers, which determine the relative position of each variable within the codebook. Users of the main Youth data will recognize these reference numbers as conceptually equivalent to the "R"/"T" numbers used in the NLSY79 main Youth documentation.

Reference numbers that start with "C" are used for data items on the Child file. The "C" numbers appear in each NLSY79 Child codebook entry and also form the basis of the variable names on the SAS and SPSS control cards that are generated by the extraction procedures on the data set.

Reference numbers for Young Adult variables are prefixed with the letter "Y." Decimals in the Young Adult reference numbers generally indicate that more than one variable has been derived from a single question. However, decimals may also appear in reference numbers when variables have been added to the file after the original public release. For example, these variables have been added to the 1994 YA data:

Multiple field instruments, in both paper and computer-administered format, have been used to collect information from and about the NLSY79 children. These instruments are used to assess the children and to elicit reports about their health, aptitudes, achievement, attitudes, relationships and behaviors. A brief description of these instruments is presented below. For more detailed information, view the following topics at the bottom of this page: Child Survey Instrument Structure & Content and Young Adult Survey Instrument Structure & Content.

The Child Supplement (CS) was a questionnaire, administered in every survey year from 1986 to 2014 to each NLSY79 child eligible for interview. The CS was used by the interviewer to obtain permission from the mother, verify age and grade, measure the child's height and weight, complete the interviewer-administered assessments, and obtain reports from school-agers about their schoolwork, work for pay and religion. The Child Supplement was the key field instrument used by the interviewer to administer the child assessments directly to the child. It contained questions about school, directed to older kids, and a section where the interviewer could record any special conditions that might affect testing. The CS was also used by the interviewer to record observations about the child's home environment. From 1986-1992, the CS was administered on paper. Starting in 1994, the CS became a CAPI (computer administered personal interview) questionnaire.

A Child Self-Administered Supplement (CSAS), introduced in the 1988 survey and administered through 2014, contained questions about family interactions, attitudes, friends, and sensitive behaviors for children 10 and older. Initially a separate instrument, the CSAS was integrated into the Child Supplement in 2006.

A Mother Supplement (MS), administered from 1986 to 2016 to the mother for each child, contained mother-report assessments and questions about health, school, and family background. A limited number of questions about child health and school were asked in 2018, but no assessments were administered. Note: Starting with the R22-2006 survey, the Mother Supplement (MS) was integrated into the mother's main Youth questionnaire but still administered in its entirety for each child. Main youth questionnaires are available on the NLSY79 Questionnaires page; the Mother Supplement sections are also provided on the Child/YA Questionnaires page.

The Young Adult questionnaire is a CAPI instrument, first used in 1994, has been used to interview all NLSY79 children once they have reached the age of 15. Beginning in 2016, children ages 12 to 14 also complete the Young Adult questionnaire. Children age 14 answer the same questions as 15 and 16 year olds, whereas the children ages 12 and 13 answer far fewer questions, many of which were in either the Child Supplement or the Child Self-Administered Supplement. From 1994 to 1998, the Young Adult survey also included a paper supplement called the Young Adult Self-Report Booklet.  Beginning in 2000, the content of this instrument was modified and incorporated into the CAPI questionnaire. In the initial YA survey rounds, the questionnaire was modeled after the main Youth instrument but has since been revised, streamlined, and updated to reflect the content areas relevant to the activities and life stages of the young adult children.

Where to View the Questionnaires. Users are urged to examine the NLSY79 Child and Young Adult data collection instruments and relevant main NLSY79 Youth questionnaires in conjunction with the other documentation that accompanies the data files. Child and Young Adult questionnaires are available in PDF or HTML form on the Child/YA Questionnaires page; main youth questionnaires are available on the NLSY79 Questionnaires page. More detailed discussions of the content of each questionnaire and the mode of administration used in the current survey are provided the Interview Methods section.

Users also need to know how to find the specific question in the survey instruments that goes with a given variable in the data set. Information about linking the data to the questionnaires is provided in the Question Names & Reference Numbers section of this guide.

Child and Young Adult structure and content

• Child Survey
• Young Adult Survey

Child Survey

Interview Dates. During the NLSY79 survey rounds in which multiple Child instruments were used, the child instruments were not always fielded on a single date.  For example, from 1986-2004, interviewers assigned to assess two or more children in a single family might ask the mother to complete one or more Mother Supplements (one MS for each child) on the first visit to the home. On that first visit the interviewer might complete one Child Supplement (CS) and one Child Self-Administered Supplement (CSAS), scheduling the remaining Child Supplements for all children until the next visit on a subsequent day. Even when the CSAS was folded into the Child Supplement in 2006, it was possible for a child to complete most of the CS (including the assessments) on one date, and then complete the CSAS section later. Starting in 2006, when the Mother Supplement was first integrated into the mothers' main interview, the date of the Mother supplement became the same as the mother's date of interview (DOI), since the mother's main Youth interview was generally completed in one session.

Fielding Periods. Historically, the field period of the NLSY79 Child and Young Adult data collection generally coincided with the main Youth. However, starting in 2002, main Youth and Young Adult telephone interviewing began substantially prior to the younger child interviews. While this fielding strategy had a positive impact on overall completion rates, it potentially widened the gap between the mother's interview and the assessments administered to her children later in the year. Fielding of the Child typically occurred over a period of about six months from late May through November or later. In some survey rounds a small number of cases were actually completed in the calendar year following the survey year.

As indicated in Table 1, child fielding has generally occurred over periods of approximately 6-9 months in each survey round; the young adult field period generally lasted somewhat longer. Until 2004, data collection was completed within the calendar year of the particular survey round. In 2004, child interviews were conducted June-December, with 15 cases completed in January-February 2005. In R22-2006, child interviews were conducted March-December, with 33 cases completed in January-February 2007. In R23-2008, nearly all child interviews were conducted April-December 2008, with 19 cases completed in January-February of 2009. In R24-2010, nearly all child interviews were conducted March-December 2010, with an additional two cases completed in January of 2011. In R25-2012, child interviews were conducted November 2012-August 2013, with more than half the cases completed in 2013. In R26-2014, all of the child interviews took place in 2015. R26-2014 was the last round of fielding for the Child as far as direct interviewing of the children; however, in R27-2016 mothers still completed Mother Supplements for children ages 0 to 13. In R28-2018, no Mother Supplement assessments were administered, but mothers answered a small number of child health and schooling questions for children aged 18 and younger.

Table 1. NLSY79 Child and Young Adult Surveys: Fielding Periods

Changes in the Child Assessments

Over time there have been changes in the administration of various assessments in the Child surveys. Details on changes in the content, administration, or scoring of particular assessments are discussed in the appropriate assessment-specific sections of this users guide (see The Child Assessments: Introduction for an overview). Two assessments, Memory for Location and Body Parts, were administered in 1986 and 1988, but have since been deleted from the data collection effort due to funding constraints. However, the 1986 and 1988 individual items and scores for these two assessments remain in the data file and are available to users.

Not all assessments were fielded in each child survey year. In some instances, assessments were administered only to children for whom no valid score has been obtained during a previous survey. In 1988 a procedure was introduced by which children ages 10 or 11 were designated to complete any assessment for which they were age-eligible in order to establish a representative index group for future analyses. Starting in 1996, the Self-Perception Profile (What I Am Like) was only administered to children ages 12 and over. The McCarthy Verbal Memory Subscale was administered for the final time in 1994. In 2004, very young children were not administered assessments, which means that scores are not available for Motor and Social Development in 2004. In 2016, only the Mother Supplement assessments were completed (Behavior Problems Index, the HOME-SF, and Motor and Social Development). The Self-Perception Profile was administered as part of the Young Adult survey in 2016 and 2018.

Young Adult Survey

By 1994, substantial numbers of children of NLSY79 mothers had reached at least mid-adolescence. Because of the enormous potential for further research possibilities with the NLSY79 cohort and their offspring, the decision was made to separate these older children into a third NLSY79 component: the Young Adults. Beginning in 1994, NLSY79 children ages 15 and older by the end of a survey year were no longer given cognitive and other assessments, but instead received a more standard Computer Assisted Personal Interview (CAPI) survey. This Young Adult CAPI questionnaire focuses on the transition to adulthood, with detailed questions on education, employment, training, health, fertility, parenting, family formation, attitudes, interactions with family members, substance use, sexual activity, non-normative activities, and pro-social behaviors. Many questions in the Young Adult survey parallel those asked of their mothers over the years, particularly when their mothers had been at comparable life cycle points. However, the Young Adult survey contains more in-depth data in certain areas such as sexual activity, drug use, schooling activities, attitudes, and marriage and cohabitation histories. The primary interview mode for the 1994 through 1998 survey rounds was in-person interviewing. Beginning with the 2000 survey round, the primary mode has shifted to telephone interviewing.

Older children who are defined as eligible for the Young Adult survey for a given round are said to be "fielded" in that survey year. Not all older children represented in the child file are eligible to be fielded as Young Adults, for a variety of reasons. Whereas the Child/Young Adult file includes all children known to have been born to NLSY79 mothers, the older children of mothers in the no longer interviewed military ;and poor white oversamples are ineligible to be interviewed as Young Adults. Additionally, children who have no child interviews or only one assessment point from very early in the child study, such as 1986 or 1988, and/or who have not been co-resident with their mothers at least part time are usually not fielded in the Young Adult sample. Generally speaking, we field older children who have either been assessed or interviewed in recent rounds, or who are currently or were typically living with their mother either full or part time during at least part of their childhood. Of course, not all of the children we field as Young Adults get interviewed. Mothers may refuse to allow younger Young Adults (under age 18) to be interviewed, the Young Adults themselves may refuse, or we may fail to locate them. 

Constraints on the Young Adult sample have changed over time as follows:

• In 1994 and 1996, the Young Adult sample included all children who were age 15 and over by December 31 of that year and who met the other selection criteria, having been assessed or living with their mom in the two previous rounds.
• Due to budgetary constraints, the Young Adult sample in 1998 was limited to youth through age 20 as of the interview date who met the other selection criteria.
• With additional funding through a grant from NICHD, since 2000 the sample again included Young Adults ages 21 and older, as well as those ages 15 to 20. The selection criteria were widened to include age eligible children with at least some assessment history; therefor, children who were age-eligible but not fielded in 1994 to 1998, but had some assessment history, were fielded for the first time in 2000.
• In 2000 only, the young adults between the ages of 15 and 20 of 38% of the black and Hispanic oversample mothers were not fielded for budgetary reasons. These Young Adults were once again eligible to be interviewed in 2002.
• Beginning in 2010, Young Adult respondents over the age of 30 have been moved to a four-year interview cycle. The interviewed sample is selected by age as of December 31 of the survey year, so that approximately half of the older young adults are eligible each round. Beginning in 2010, young adults age 31-32, 35-36, 39-40, 43-44, etc., as of December 31 of the survey year are not fielded.
• Beginning in 2016, the fielding age for the Young Adult was lowered so that children ages 12 and older were fielded. This ensured that we collected some of the same information from the children who would have been age-eligible for the Child Self-Administered Supplement had the Child been fielded. Children age 14 answered the same questions as those ages 15 and 16, while those ages 12 and 13 answered far fewer questions.