NCDS response and missingness

Find out more about the level of response for every sweep of the 1958 National Child Development Study, important predictors of non-response, and how to handle missing data in the study.

As of September 2026:

• Of the 17,415 cohort members who participated in the first sweep, 3,898 (22.4%) have participated in all 12 major sweeps.
• Of all 18,558 cohort members, 12,619 (68.0%) have taken part in at least half the sweeps (six or more sweeps).

NCDS response (1958-2020)

The table below presents statistics about response in NCDS at every major sweep from birth.

Table: Participation in NCDS from birth to 62 years

	Total cohort	Dead	Emigrants	Eligible sample	Participants	(% of eligible sample)
Birth – 1958	17,633	0	0	17,633	17,415	98.8
Age 7 – 1965	18,010a	821	475	16,714	15,425	92.3
Age 11 – 1969	18,283a	840	701	16,742	15,337	91.6
Age 16 – 1974	18,558a	873	799	16,886	14,654	86.8
Age 23 – 1981	18,558	960	1,196	16,402	12,537	76.4
Age 33 – 1991	18,558	1,049	1,335	16,174	11,469	70.9
Age 42 – 2000	18,558	1,199	1,268	16,091	11,419	71.0
Age 44 – 2002	18,558	1,286	1,236	16,036	9,377	58.5
Age 46 – 2004	18,558	1,323	1,272	15,963	9,534	59.7
Age 50 – 2008	18,558	1,459	1,293	15,806	9,790	61.9
Age 55 – 2013	18,558	1,659	1,286	15,613	9,137	58.5
Age 62 – 2020	18,558	2,447	1,526b	14,585b	8,215b	56.3

^a At ages 7, 11 and 16, the original sample was supplemented by migrants born in 1958.

^b At age 62, 327 cohort members known to be living outside of Great Britain (emigrant cases) were invited to take part in the mop-up web survey, of whom 190 responded. Such emigrants are not formally considered as part of the NCDS target population, so to maintain consistency with earlier sweeps they have been considered as ineligible in these calculations (and those preceding the table), though their data are available for analysis.

Figure 1: NCDS response (as % of eligible sample) over time

Missingness in NCDS

Missing data are common in surveys and cohort studies. To tackle this in NCDS, we have used a systematic data-driven approach to identify variables that are important predictors of non-response at each sweep.

We have used a systematic data-driven approach to identify variables that are important predictors of non-response at each NCDS sweep, between age seven and age 55. Future work will extend this analysis to include non-response at the age 62 sweep.

A list of these variables is provided in the appendix of the Handling missing data in the CLS cohort studies user guide.

These variables can then be considered for inclusion in analyses – for example as auxiliary variable when using multiple imputation – in order to maximise the plausibility of the missing at random (MAR) assumption.

Read more about the process in the article: Missing at random assumption made more plausible: evidence from the 1958 British birth cohort.

Example: restoring the composition of NCDS at age 50 and 55

We have been able to restore the composition of the NCDS samples at ages 50 and 55 to be more representative of the study’s target population. We did this by including predictors of non-response at age 50 and age 55 as auxiliary variables in multiple imputation analyses.

For example, we were able to replicate:

• the original distribution of paternal social class observed at the birth survey
• the distribution of cognitive ability at age seven
• the known population distribution of educational attainment and marital status at age 50.

Figure 2: Social class of mother’s husband at birth before and after adjustment for missing data

The imputation phase of this analysis included predictors of non-response at age 55 and social class at birth only for cohort members that participated at age 55.

Figure 3: Percentage of those with degree or equivalent at age 50 in the Annual Population Survey and NCDS before and after adjustment for missing data.

APS GB: Annual Population Survey = Born in Great Britain in 1958, derived by the Office for National Statistics (ONS)

APS All: Annual Population Survey = Born in Great Britain or elsewhere in 1958 (derived by ONS)

NCDS50 MI: Estimate after multiple imputation using predictors of educational attainment at age 50 and predictors of non-response at age 50 as auxiliary variables.