NCDS7 (2004)


The 2004/2005 follow-up extended the data collection of the previous NCDS surveys in line with the Forward Plan for the cohort studies, developed in 2002 by the then Director of CLS, Professor John Bynner.  This sought to integrate the timing, design and analysis of future surveys of NCDS and BCS70 – taking account of the sequencing of Britain’s third birth cohort study, the 1946 cohort (NSHD, housed at UCL). This would enable comparisons between cohorts born at different times, or between different age groups at the same point in time.

In 2004, CLS was granted long-term funding as an ESRC Resource Centre to establish a stable infrastructure for the study and ensure that fieldwork is conducted at regular intervals.

The Centre for Longitudinal Studies led the development of the 2004/5 survey and commissioned the fieldwork.  This latest sweep was conducted for the first time as a telephone interview, when the cohort members were 46 years of age.

Funding

Fieldwork was funded by the Economic and Social Research Council (ESRC).

Design

The main aim was to update information gathered previously, in order to explore factors central to the formation and maintenance of adult identity in each of the following domains:

• Lifelong learning
• Relationships, parenting and housing
• Employment and income
• Health and health behaviour
• Citizenship and values

As with previous NCDS follow-ups, the surveys were designed in collaboration with advisors drawn from researchers, policy makers and funders.

Survey Instrument

The NCDS 2004/2005 survey used a single a 30-minute Computer-Aided Telephone Interview (CATI) for all cohort members.  Proxy interviews were not permitted during this latest round of the NCDS, unlike in earlier adult follow-ups. 

Fieldwork

Following competitive tendering, the National Centre for Social Research (NatCen) was commissioned by CLS to carry out both the 2004/2005 NCDS telephone survey and the BCS70 2004/5 face-to-face survey.  NatCen’s responsibilities were to work in collaboration with CLS in the development of instrumentation, carrying out the data collection and initial data preparation, as well as supplementing CLS tracing activities, and making contact with cohort members.

The target sample for the NCDS telephone survey comprised 11,739 cohort members.  To remain within the available budget, the target sample was selected to minimise administrative efforts.  Details of cohort members who had refused further participation, and those who had emigrated or died were not issued to NatCen.  Those who had not participated in any survey since 1981 were also excluded from the target sample.

The main data collection took place between June 2004 and November 2005. It had originally been scheduled to be completed within nine months but was extended when early fieldwork showed that a relatively high proportion of cohort members had moved and needed to be traced to new addresses. In total 80% of the telephone interviews were carried out during 2004.

Data coding and editing

The NCDS telephone interview included a number of open-ended questions where the verbatim answers of cohort members are keyed by interviewers, and a rather larger number of questions where precodes are provided for answers but provision is also made to record additional information where then precode ‘other’ is used.  Following the start of the survey, these questions were reviewed by the CLS team in order to determine the priorities for coding, and to identify the appropriate coding frames.  Where possible, coding frames that had been employed for earlier NCDS surveys were adopted, although it was usually necessary to include additional codes.  In other instances, it was necessary to develop a coding frame from scratch. Coding was undertaken by NatCen.

A major advantage of the use of CATI is the reduced need for post-fieldwork editing – the majority of checks for validity, range and consistency can be incorporated into the CATI/CASI program.  Inevitably, however, there were checks which were overlooked, or not initially thought necessary.  These checks were incorporated into the data processing activities undertaken by NatCen after the survey.