NCDS useful notes
This page contains a selection of the NCDS queries sent to the ESDS Longitudinal help desk which may be useful to
other users. Each query has been anonymised and some have been edited.
If you have any useful information about NCDS data which you think others may benefit from reading, please
contact the ESDS Longitudinal help
desk and it will be considered for inclusion. If your text is only rough, we will check it and tidy up wording as
These notes cover NCDS generally. Further information is available in the documentation of the individual NCDS datasets.
Data availability related questions
Multi-wave data related questions
Household/family composition related questions
Health/health behaviour related questions
Education/economic activity related questions
Q - I would like to use the variables “medical examination” (N1461) and “educational questionnaire” (N2092) but they are not in the datasets I downloaded. Are these variables available? (March 2010)
A - These variables and others are in SN 5744 -National Child Development Study: Local Authority Data, 1958-1974: Special Licence Access.
Q - Some of the Clinical Interview Schedule (CIS-R) questions listed in the documentation for SN 5594 -National Child Development Study: Biomedical Data, 2002-2004: Special Licence Access such as the IDEA and SUIC variables are not in the dataset I downloaded. Are they available? (March 2010)
A - These data are available directly from the depositor. Please contact the Centre for Longitudinal Studies for further advice.
Q - I have downloaded SN 5566 National Child Development Study: Sweep 4, 1981, and Public Examination Results, 1978 and cannot find the ‘exam entries’ 13-digit codes mentioned in the associated coding frame. Are these codes available? (August 2009)
A - No, the data were recorded on magnetic tape but were not transferred in 13-digit form to the deposited dataset. However, the deposited ‘exams’ dataset does contain key subject and grade information.
Q - Can I get information on the genotype data associated with the NCDS? (May 2009)
A - The genotype data are managed separately. For further information please see www.b58cgene.sgul.ac.uk/index.php.
Q - Can I access the 1946 Birth Cohort data through the UK Data Archive? (December 2007)
A - No, those data are not deposited with us. You will need to contact the MRC National Survey of Health and Development for details on how you might access the material (http://www.nshd.mrc.ac.uk/nshd.aspx).
Q - I have downloaded SN 5578 -National Child Development Study: Sweep 6, 1999-2000 . The User Guide Vol. 1 refers to a number of derived variables that are not in the data I downloaded. How can I obtain these variables? (August 2007)
A - Those variables are not included in the dataset but the derivation details and codes to create them are found in Appendix 4 of the User Guide. Similarly for other NCDS studies, derived variables are not always included in the associated datasets but the documentation will describe how users can create them.
Q - Does the condition "I agree not to link between the research identifiers supplied by ESDS [NCDSID] and any other identifiers previously issued" mean that I am not permitted to link the waves of the NCDS? (March 2010)
A - No, you can still link to previous waves but you need to be aware that a new linking variable was created in Spring 2008 (MCSID) to replace the previous identifier (SERIAL). All earlier datasets that contained the old identifier were replaced with new editions that now contain the new variable. Therefore, you should download the latest editions of earlier waves to ensure that you can continue to link the latest sweep with preceding years of the survey. Further information is available in the CLS Confidentiality and Data Security Review Document.
Q - I am using NCDS Sweep 3 and want to identify cohort members living in one parent families but there is no variable that indicates this. Is this possible? (January 2008)
A - This can be done indirectly using variables n2371 to n2377 which describe the relationship of the person acting as the cohort member's mother.
For N2371 3P Relationship-person acting as mother, one of the values is 'None regular' and by crosstabulating with n2375 on fathers you can deduce who is living with a lone mother or a lone father and variables such as n2372 record the reason (e.g. death, divorce, separation).
Q - Is the age of the mother and father, the age at the time of birth or at the time of interview? (October 2007)
A - The variable gives the age at the time of interview. This would have taken place as soon as possible after birth and within the same week.
Q - Is birthweight information included in the NCDS? (April 2010)
A - Yes. If you use SN 5565 ‘National Child Development Study: Childhood Data, Sweeps 0-3, 1958-1974 , the birthweight variable is n646.
Q - I have downloaded Sweep 7 of the NCDS and found that there was no cohort weight information. Have these variables been eliminated? (January 2010)
A - The data depositors at the Centre for Longitudinal Studies did not include weight information because of reliability issues of using self-reported weight in telephone interviews and because the biomedical data had been collected only two years prior to Sweep 7.
Q - Does the NCDS contain variables about drug use? (July 2008)
A - Yes, a search of the Online Data Dictionary on the CLS web pages reveals a number of relevant variables:
- NCDS3: Third Follow-up, 1974 (Cohort age=16 years), Medical Questionnaire, question on 'Reason for hosp admiss last 12'
- NCDS4: Fourth Follow-up, 1981 (Cohort age=23 years), NCDS4 Derived Variables (Developed by the NCDS4 team 1981-4), 'Drug dependence'
- NCDS5: Fifth Follow-up, 1991 (Cohort age=33 years), Cohort Member Interview, 'CMI:79 ...'
- NCDS & BCS70 1999-2000 Follow-ups,
'MORE31 (SC) Taken more than 1 other drug?'
'DRUG2 (SC) Name of 2nd other drug not mentioned'
'DRUG17 (SC) Taken 6th other drug in the last 12 mths?'
'DRUG6 (SC) Name of 6th other drug'
Q - Was the mother’s weight recorded? (April 2008)
A - Yes, this is recorded by variable n496 in SN 5565 National Child Development Study: Childhood Data, Sweeps 0-3, 1958-1974.
Q - Can the Malaise Inventory be found in the NCDS? (March 2006)
A - Yes, for NCDS4 (part of SN 3148), the variables are N6016 through N6039 (found in data file NCDS4.***). For NCDS5 (also part of SN 3148), the variables are N504237 through N504261 (found in data file CMI.***). For NCDS6 (part of SN 4396), the variables are MAL01 through MAL24.
Q - When mothers in the study are asked if their children were born early or late, what is the reference point? (October 2006)
A - There was no specified reference point in terms of weeks. Instead the respondents answered this question according to the date they were advised or believed the baby would be born.
Q - Some of the derived economic activity variables in NCDS4 such as ec194 and ec286 have abbreviated responses. What do they stand for? (May 2010)
FT JOB = full-time
FTJ = full-time
PT ED = part-time education
APP = apprenticeship
DBR TC = day/block release training course
FTTC = full-time training course
TOPS = Training Opportunities Scheme
LGSS = Local Government Special Scheme
FTEDPOSTSCHL = full-time education post school
FT NT TOPSTC = full-time not Training Opportunities Scheme
OLF = out of labour force
Q - The ‘highest qualification’ variables in the ncds5cmi file of NCDS Sweep 5 are confusing. Should I be using variables n501150 to 501170? (May 2010)
A - Although the variables n501150 to n501170 from the cmi (‘cohort member interview’) are referred to as ‘highest qualification’, this is rather misleading, as it is not necessarily the highest qualification they have ever achieved. If you look at the questionnaire on page 71 of the pdf (or p23 as printed on the top of the page), you will see that the instruction which gives rise to those variables is ‘Ask questions B4a) to B9e) about courses designed to lead to qualifications and access courses since March 1981. If more than 2 courses, identify the two designed to lead to the two highest qualifications...’. So there may have been other qualifications achieved before 1981 (i.e. before NCDS4) which were higher than these.
Variables n501441 to n501469, ask the respondent about their overall highest qualification. These are the best variables to use.
Q - I am having difficulty interpreting the edqtyp and voctyp variables in NCDS Sweep 6. What, for example, is the difference between edqtype01 and edqtype14? (April 2010)
A - The variables edqtyp01, edqtyp012, ... edqtyp14 etc., are ‘multicode’ variables (that is what the MC stands for). If you have a look at questionnaire, the relevant section is on page 95:
The respondent is shown a card on which is listed all the different types of academic qualification they might have achieved since the ‘reference date’, which is basically the date they were last interviewed (March 1991 if interviewed at NCDS5; otherwise March 1974).
There are 13 ‘multicode’ slot variables because the respondent may have more than one qualification. You should note that the variables edgtyp01 to edqtyp13 are only used in the case of ‘proxy’ replies (i.e. where the cohort member is unable to reply for themselves and someone else responds on their behalf). So the important variables are edqtyp14 to edqtyp26, which apply to the vast majority of people.
Similarly, the variables voctyp01 to voctyp11 are multicoded variables looking at which of 11 possible types of vocational qualifications they might have received since last interviewed. Again, these are the ‘proxy’ variables, and the ones which apply to the vast majority of respondents are voctyp12 to voctyp22.
Q - Where can I find an explanation of the employment codes in SN 5600 National Child Development Study: Employment Histories, 1974-2000? (June 2009)
A - Please see the Data Note 2007/1. On pages 6 and 10 of the PDF, you will find an overview of the employment and occupation details. The classifications used are CO80 (NCDS 4) and SOC90 (NCDS 5 & 6).
Q - I am using NCDS sweep 6 and am unclear as to how the variables relating to highest educational qualifications are derived. Where can I find this information? (October 2005)
A - The syntax used to create the highest educational qualification variable is found in Appendix 7 of the User Guide.