This appendix details the development of the NLSY79 questionnaires and codebooks.
In 1992 (round 14) and prior survey years, interviews were conducted by Paper and Pencil Interviewing (PAPI). Computer-Assisted Personal Interviewing (CAPI) technology was introduced in a small experiment in 1989 (round 11) and a larger experiment in 1990 (round 12). Round 15 (1993) marked the first round of the National Longitudinal Survey of Youth 1979 to be administered entirely using CAPI technology. Wherever possible, comparability was maintained between the 1993 data documentation and that of previous survey years. However, continuous innovations in technology and certain data collection procedures have resulted in considerable improvement in the format and content of electronic questionnaires and codebook documentation. A number of these transformations are outlined below.
Questionnaire innovations
Technological advancements in CAPI survey software have facilitated efficiencies in the conduct of interviews that were not possible with the PAPI instruments. Some significant advancements that accompanied the transition to CAPI data collection have included:
- the availability of specialized question types, allowing for more precision in data entry and processing.
- automated accessing of information reported earlier in the survey, eliminating the need for interviewers to search back through the questionnaire or keep track of earlier responses to reference them in later questions;
- automated text substitutions ranging from gender pronouns to large substantive texts that vary based on circumstance;
- replacement of most hard-copy QxQ material with electronic help screens, linked to individual relevant questions;
- imposition of minimums and maximums for many numeric questions, reducing the instances of erroneous outliers;
- "bounded interviewing" - minimum/maximum values for dates, similar to those set for numeric questions; bounding of dates drastically reduces if not completely eliminates, anomalies such as job gap dates that precede the appropriate start date or exceed the appropriate stop dates, start dates that exceed interview dates, etc.
- structured rostering of records pertaining to groups that are the subject of inquiry, such as employers, children, household members; the roster organizational structure provides more efficient storage of data related to the individual employers/children/etc., as well as clarity in presentation to the interviewer on the computer screen.
- question loops: Loops are repeating sets of questions, asked about different subjects of inquiry. For example, series of similar or identical questions that need to be asked about each appropriate subject in a group (employer/child/household member/etc.) can be programmed in loops. The electronic instrument then cycles through these loops containing very similar or identical questions for each individual subject in the group. Loops reinforce the uniformity of data collection about each unit of observation in a group. Finally, question loops allow for expansion of the number of subjects or events in an event history that can be collected without adding potentially substantial volume or complication to a hard-copy questionnaire. In PAPI survey years, the number of columns available in the hard-copy questionnaires to collect information on subjects such as household members, children, gaps in employment, training programs, etc. were finite -- limited by space on the page. This limitation disappeared with the use of electronic questionnaires. This feature also allowed the expansion of the recipiency questions to a more extensive event history.
- additional functionality of electronic questionnaires; Mechanical data checks that filter respondents into correct questions and the capability to sort individual subjects organized in a roster, combine with question loops to help ensure that questions are administered about the correct subjects in the correct order. For example, rostering and sorting ensure that the "current/most recent employer," referred to historically as the "CPS employer," is always asked about in the first loop of questions. Although this has always been the intention, recording and processing errors in PAPI years resulted in occasional cases for which the CPS employer was not entered as the first employer.
Data and documentation innovations
Continuing enhancements to CHRR's Designer CAPI software have made possible several more advancements in the presentation of data and documentation as well. These include:
- increased uniformity in question naming conventions, improving the ability to identify comparable questions across survey rounds; In PAPI survey rounds (1979-1992) question names changed with each round. The evolution of Designer CAPI software also entailed several rounds of changes in question naming formats. CHRR personnel have been working as schedules and manpower allows, to eliminate question name inconsistencies resulting from these multiple transitions. This effort is on-going with additional progress reflected in each successive public release.
- improvement in assignment of more precise areas of interest. Multiple areas of interest can be assigned to variables that make sense in more than one substantive category. In addition, areas of interest (particularly large and/or more generic ones) can be broken down into more precise and meaningful categorizations. Adjustments to area of interest assignments are part of an on-going effort, similar to that described above with respect to question naming.
- greater ease in documentation capability. Vastly improved documentation features in the software have allowed sets of created variables of considerable size (Work History week-by-week arrays and the Employer History roster for example) to be incorporated into public release data sets relatively smoothly.
Continuing data and documentation enhancements
As noted above, changes in interviewing modes and rapid technological innovation led to some inconsistencies in documentation over the history of the survey. Many of these inconsistencies have arisen because of modifications in the conventions for question naming, assignment of areas of interest and formatting of various documentation components. CHRR personnel are working continually on updating documentation to increase comparability of documentation through survey years, and increase user-friendliness of the data and codebook.
Comparability in Data Presentation: "Consolidated" Variables
An effort was been made in the 1979-1993 data release to maintain comparability with PAPI data releases in terms of data presentation. Toward this end, some sets of variables have been "consolidated." In other words, the responses for multiple variables are collapsed into a single created variable or set of variables. This has been done primarily for variables that in previous years were a single data item or set of data items, but are collected in more than one variable or set of variables in the CAPI questionnaires.
In each case, the variables being consolidated are mutually exclusive with respect to substantive responses. In other words, if variable A, variable B and variable C are consolidated, respondents will have given a response to only one of these - either variable A, or variable B or variable C.
Consolidation spares users from having to access a larger number of variables and use each separately or combine the responses themselves.