The Value of Longitudinal data: using the British
Cohort Studies to understand women’s employment
from a life course perspective
Dr Jane Elliott
Research Director (NCDS and BCS70)
Centre for Longitudinal Studies
29th June 2006
www.cls.ioe.ac.uk
Structure of presentation
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The four British Birth Cohort Studies
The value of cohort data
The 1958 cohort (National Child Development Study)
Gendered aspirations at age 11 (combining qualitative
and quantitative methods)
Occupation and Fertility
Women’s employment behaviour after the birth of a child
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British Birth Cohort Studies

Fully representative samples of the British population
Based on one week’s births - approximately 17,000 babies
Followed up from birth into adulthood
Four British Birth Cohort Studies

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1946 : National Survey of Health and Development (MRC
funded)
1958 : National Child Development Study
1970 : British Cohort Study 1970
Housed at
2000/1: Millennium Cohort Study
CLS
www.cls.ioe.ac.uk
1958 Birth Cohort Study




Representative sample of over 17,000 infants born in March 1958
Not initially planned as a longitudinal study
Sample followed at ages 7, 11, 16, 23, 33, 42, 46 (prospective study)
Retrospective life history data collected at age 23, 33, 42, 46
 For example
 work history
 partnership history
 fertility history
 housing history
 Approximately 12,000 individuals are still participating
 Information on individuals can be linked from birth and childhood
through into adult life
 Now funded by ESRC with data collected every four years
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NCDS follow-ups and sources of information
Notes
a: Target sample - Excludes emigrants, refusals & deaths. Includes immigrants at NCDS1-3.
b: Achieved sample - At least on survey instrument partially completed
c: Mother - Could be Cohort Member or spouse/partner
Hypothetical life history
Exam
results
Aspirations
Parents’ social
class
Training and
skills
Parental
divorce
Born
1958
x
Age 7
Age 11
Age 16
Voting
behaviour
Savings
Gets married
1st Child
2nd Child
1984
1981
Age 23
1987
1991
Age 33
2000
2004
Age 42
Age 46
Mother
smoking
Job 1
Parental
interest in
school work
Free school
meals
Job 2
Job 3
Psychological
well being
Maths and reading
tests
Domestic division
of labour
Working hours
preferences
Union membership
Teachers’ assessment of
child’s behaviour
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Research questions best addressed by cohort data


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Long term outcomes of experiences and decisions in
early life
Medium and short-term outcomes & links between
different life domains (e.g. health and employment)
Descriptions of individual trajectories – careers,
relationships, fertility, poverty and disadvantage
The links between social change and the changing
experiences of different cohorts
Intergenerational transmission of advantage and
disadvantage and the processes involved
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NCDS 11-year old Essays




At age 11, in 1969 NCDS Cohort members completed a short
questionnaire (at school) about leisure interests, preferred
school subjects and expectations on leaving school
They were also asked to write an essay on the following topic:
‘Imagine you are now 25 years old. Write about the life
you are leading, your interests, your home life and your work
at the age of 25. (You have 30 minutes to do this).’
13669 essays completed, mean length 204 words
Copies of the original essays (in children’s handwriting) are
available on microfiche at CLS and are currently being
digitised.
www.cls.ioe.ac.uk
Existing research on the essays



A small sample of 521 essays have been coded for word
count
 Boys 180 words
 Girls 228 words
All essays have been coded for employment aspirations, over
90% give a classifiable occupation
No other systematic coding and analysis of the essays has
been carried out to date
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Research project funded by the Nuffield
foundation (Elliott and Morrow)
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
Project is intended as a pilot study, if successful to be followed up by larger
application to ESRC
Aim to type up and code a sub-sample of 560 essays & conduct preliminary
descriptive analyses
Sample stratified to reflect: gender; ability; social class; family structure
Essays will be coded for themes such as:
 family life; leisure; employment; housing expectations; contact with parents;
pets; transport and travel; aspirations vs expectations
Both qualitative and quantitative analysis will be carried out using NVIVO.7 and
SPSS to help organize, code, and analyze the data
Main research questions: how do gender and social class shape children’s
aspirations?
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Home experiences

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46% of the eleven-year-olds were living in owner-occupied
accommodation while 42% were in council housing
44% of children had their own bedroom
19% of girls and 16% of boys shared a bed with another member of
the family
61% of mothers reported being in work at some time since the child
was seven (only 3.2% were in professional or managerial occupations,
compared with 20% of fathers)
66% of mothers reported that the father took an equal role in
‘managing’ the child and a further 24% described the father as having
a significant role
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School experiences (1969)
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The majority of children were in primary schools when
they wrote the essays
Only 4% of children were at independent schools
At age 11 the median class size was 36 pupils (mean
34.3), while at age 7 the median class size had been 37
with a mean of 35.25
82% of children were in a school with a male headteacher
45% of children had a female class teacher
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Aspirations of boys and girls at age 11top 10 occupations
30.0
25.2
25.0
Boys
Girls
842 boys and 375 girls
expressed aspirations for a
professional occupation in
their essay at age 11.
15.0
14.3
15.0
12.2
12.1
11.6
11.4
9.4
10.0
8.5
6.3
5.6
5.4
5.8
5.0
2.5
1.9
2.8
1.7
1.0
0.4
0.0
Occupation
as
si
st
an
ts
e
Sh
op
ur
s
N
.e
.c
O
th
er
w
or
kn
se
rv
ice
Pe
rs
on
al
en
,w
om
en
II
Sp
or
ts
m
no
n-
m
an
,S
C
al
th
O
Ty
pi
st
s,
cl
er
ic
et
c
Te
ac
he
rs
Pr
of
es
si
on
al
et
c
ille
d
m
an
ua
l
0.0
Sk
Percentage
20.0
Impact of ability and gender on aspirations for a professional
occupation
25.0
Boys
Girls
19.7
% professional aspirations
20.0
15.0
11.8
10.0
10.0
5.5
4.6
5.0
2.2
0.0
Low
Medium
General ability
High
Impact of family background and gender on aspirations for a
professional occupation
25.0
Boys
Girls
% with aspirations for a professional occupation
20.0
20.0
15.0
10.0
8.7
9.5
8.4
4.0
5.0
4.2
0.0
Non-manual father
Manual father
Family Background
No father
Preliminary analysis (139 essays coded)

Girls are slightly more likely than boys to say they
will be married at age 25 (56% vs. 48%)
 Girls and boys are equally likely to say that they
want children (45% vs. 42%)
 Girls are more likely than boys to write about
domestic labour (65% vs. 25%)
 Girls are more likely than boys to mention their
husband/wife’s occupation (20% vs. 10%)
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282044A
I am making dinner for Paul my husband and Sally my young daughter. I think I will
make us all Shepherds pie and carrots. I car hear him coming down the garden path,
I had better hurry up. “Hello Kathyryn what are we have-ing for dinner?,” asked Paul
has he walked into the kitchen. I brought Sally in from the garden and wash her
hands, then sat her in her high chair. “Has every-thing been aright at the shop?”
Paul works in a butchers shop and he has just been promoted to the manger of five
will known shops. After we had eaten the shepherds pie and Sally had eaten her
bacon and chicken baby food I started serving the blomonge.
Serial number: 110335Y
I am 25 years of age, I live in a big house it has five bedrooms, dining
room, lounge, and kitchenet. I have a wife and two children, a big jagur
car which is just big enough to hold the family. The children are two boys,
very energetic, they love swimming and rugby. My wife is a type that can
mix with anybody, she is a good bridge, and very pasent, she is a good
nurse when the children hurt themselves. The names of the family are
Brian, Kevin, the twins, Edith my wife and me, Bobby. The doors of the
house are orange and round the windows of the door white, the window
frames are painted cream. We have oil fired central heating and an
electric cooker, and strip lighting in the kitchenet. My wife does not work
because I bring plenty money home from were I work, I work at the
catterpiller factory at Birtleys I work as a pot spot welder, because I do the
work of putting the holds through the bits of steel that make the
catterpiller tracks. Each piece of steel weighs 1 ton each. I get payed
£31 a week and the firm payes my petrol bill.
223004D
I have two children one 4 the other 6. I am working in a school
as a teacher. My husband is an Estate Agent. In the evenings
we have tea and each person tells the rest about any
interesting avents which has happened to them. Then we
have a sit and talk about what we are going to buy or if we are
going to buy a house or not. We then watch Calendar and the
news. At half past seven the children will have a bath and be
put to bed. Meanwhile my husband will be seeing that the
car’s engine is all right so that we shall not be stranded any
where is something goes wrong. After that I shall do the
ironing or washing or any other jobs that want doing. At Eleven
oclock we shall go to bed and get up at seven oclock. At eight
oclock I would take the children one to school with me the
other to her granma’s. My husband goes to work at nine
o’clock. At school I [illegible] teach first English, Maths and Art.
In the afternoon P.E., Projects and History.
The salience of occupation

Understanding heterogeneity of women

Recognise differences between women in terms of
fertility and working patterns
 Move away from voluntaristic accounts and notion
of innate differences
 Crompton & Harris suggest that occupations may
provide ‘a major social filter through which the
lives of individuals and families are
structured’(1998 p 299)
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Professionals vs. Managers

Professionals
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License to practice/credentials obtained externally
Long term planning of career possible
More flexible working arrangements
Educated to at least degree level
Managers
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Careers forged in organisation
Careers less well planned
Fewer opportunities for part-time work
May not be so highly educated
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Cross-national work by Crompton and
Harris focusing on bankers and doctors


Occupation impacts on the way that women
combine paid employment and family life
Compared with professionals, managers

Have fewer children
 Adopt less traditional division of labour
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Results from Crompton and Harris crossnational study

% of women with two or more children



Doctors
Bankers
54%
32%
% of women with a traditional domestic division of
labour


Doctors
Bankers
From
73%
46%
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Limitations of Crompton and Harris’
empirical work

Relatively small (non-random) sample
 Focus on case study of retail banking vs medical profession
 Differences between the two groups in terms of
 Professionals vs. managers
 Public vs. private
 Levels of feminisation
 Levels of qualifications
 Cross-sectional study
 Analysis of NCDS data can ameliorate many of these
problems
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Analyses using NCDS (1958 cohort)

Advantages of using NCDS

Bigger & more representative sample
 Longitudinal data & ability to control for fertility
aspirations
 Multivariate analysis predicting having children

Logistic regression including occupation, views on
having children at age 23, level of highest qualification
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Occupational variations in number of children

Data from Crompton and Harris study
 % women with two or more children
 Doctors
54%
 Bankers
32%
 Data from NCDS (1958 cohort)
 % of graduate women with children
 Professionals 75%
 Managers
64%
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Predicting who has had children
B
S.E.
Sig.
Want kids (age 23)?
Exp(B)
0.00
Don't know
-1.37
0.16
0.00
0.25
No
-2.12
0.14
0.00
0.12
SOC90 Major group
0.00
Managers (ref cat)
ref
ref
ref
ref
Professionals
0.34
0.17
0.04
1.40
Assoc prof & tech
0.43
0.15
0.01
1.54
Clerical
0.31
0.13
0.02
1.37
Craft & related
0.72
0.32
0.03
2.05
Personal service
1.33
0.18
0.00
3.78
Sales
0.81
0.20
0.00
2.26
Machine operatives
0.87
0.30
0.00
2.39
Other
1.40
0.26
0.00
4.05
Not working
1.02
0.15
0.00
2.78
Degree by age 42
-0.43
0.12
0.00
0.65
1.32
0.11
0.00
3.76
Qualifications
Constant
N=4934 women aged 42 from NCDS sweep 6
Manager or professional at 42 by domestic division of labour
Manager or profess ional
at 42?
manager
profes sional
Total
Count
% within manager or
profes sional at 42?
Count
% within manager or
profes sional at 42?
Count
% within manager or
profes sional at 42?
Domestic divis ion of labour
traditional non traditional paid help
38
35
10
Total
83
45.8%
42.2%
12.0%
100.0%
138
121
19
278
49.6%
43.5%
6.8%
100.0%
176
156
29
361
48.8%
43.2%
8.0%
100.0%
N=361 graduate women aged 42 from NCDS sweep 6
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In summary

NCDS (1958 cohort study) shows
 Differences in family building between managers
and professionals
 No differences in domestic division of labour
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Women and employment: previous research

Major change in British society since the 1950s has been increase in
numbers of women in the labour market
 A growing body of research has focused on the length of time between
childbirth and returning to paid employment.

Joshi and Hinde (1993);Dex, Joshi, Macran, McCulloch
(1998); Blank (1989);Joesch (1994)

Emphasise that the age of the youngest child is the most important
determinant of women’s participation.
 Highly educated women display the greatest continuity in employment
across the childbearing years.
 Growing polarisation between women
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However...

The majority of existing research has

not distinguished between part-time and
full-time employment
 not fully exploited the temporal features of
longitudinal data
 not explicitly looked at duration effects
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Key Research Questions

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

Are the processes of returning to part-time work and full-time
work different?
Is part-time employment a bridge into full-time employment?
Are there significant duration effects such that the longer a
woman stays out of the labour market the more difficult it is for
her to return?
Are there significant interaction effects between duration and
other variables. i.e. do the influences of some factors change
over time within individual careers?
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Research approach


Uses retrospective life history data from NCDS to focus
on women’s employment and fertility careers
Examine transitions between episodes of





Full time employment
Part-time employment
Non-employment
Emphasis on duration effects and time varying covariates
Focus on whole work history since leaving full time
education, not just on transitions after child birth
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State Transition Matrix based on women’s work histories from the
National Child Development Survey
Origin
state
Full-time
work
Part-time
work
Not
employed
Total
Destination state
Full-time
work
-
Part-time
Not
Censored Total
work
employed
episodes
7293
518 (7.1%) 4889 (67%) 1866
485
(12.8%)
2351
(35%)
2836
-
1767 (47%) 1522
3774
2851 (42%) -
1498
6700
3369
4886
17767
6656
State Transition Matrix based on women’s work histories from the
National Child Development Survey
Origin
state
Full-time
work
Part-time
work
Not
employed
Total
Destination state
Full-time
work
-
Part-time
Not
Censored Total
work
employed
episodes
7293
518 (7.1%) 4889 (67%) 1866
485
(12.8%)
2351
(35%)
2836
-
1767 (47%) 1522
3774
2851 (42%) -
1498
6700
3369
4886
17767
6656
Approach to Event History analysis

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
Data is available for each month of women’s life histories between age
16 and 33.
This data was discretised to form a data matrix
Logistic regression was used to estimate models to indicate which
factors were associated with transitions back into the labour market.
Logistic regression models do not allow for the link between
woman/months at the level of the individual woman.
More sophisticated ‘mixture’ models i.e. random effects models were
therefore estimated using the SABRE software to exploit the structure
of the data.
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Models estimated

Models estimated focused on moving back into the labour market

not employed -> full-time
 not employed -> part-time
 part-time->full time

Logistic regression models initially estimated showed negative duration
effects (i.e. pooled cross sectional models)
 Mixture models estimated allowing for unobserved individual
heterogeneity indicated that the initial models were miss specified
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Summary of main results from mixture models
Part-time -> Not emp. - > Not emp. ->
Full time
Full time
Part time
Age of youngest child
Partner
Qualifications
Duration
Duration * well qualified
National unemployment
+
+
n.s.
n.s.
-
+
+
n.s.
-
+
+
+
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Probability of returning to part time work after the
birth of a first child
.014
.012
.010
.008
.006
.004
Degree
.002
.00
No qualifications
1.00
2.00
3.00
4.00
5.00
6.00
Age of youngest child and duration out of employment (years)
Figure 1
Probability of returning to full time work after the
birth of a first child
.010
.008
.006
.004
.002
Degree
0.000
.00
No qualifications
1.00
2.00
3.00
4.00
5.00
6.00
Age of youngest child and duration out of employment (years)
Figure 2
Probability of returning to part-time or full-time work
after the birth of a first child
Women w ith degrees
.014
.012
.010
.008
.006
Part-time w ork
.004
.00
Full-time w ork
1.00
2.00
3.00
4.00
5.00
6.00
Age of youngest child and duration out of employment (years)
Figure 3
Narrative elements of cohort studies





Allow us to trace lives through time & understand how
childhood circumstances may impact on adult outcomes
In the 1958 cohort study, essays at 11 provide insights
into children’s own narratives about their lives
Potentially allow for the construction of individual case
studies based on detailed information collected over the
years (while preserving confidentiality)
Allow for a focus on the historical context which has
helped shape individual experiences
Comparisons between cohorts can enable the
development of a narrative about social change
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