educational attainment, labour market conditions and the timing of first and higher-order births in...
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Educational Attainment, Labour Market Conditions and the Timing of First and
Higher-Order Births in Britain
Andrew Jenkins, Heather Joshi&
Mark Killingsworth
EALE Conference, Amsterdam,Sept 2008
Research: Aims
• Compare timing of births in two British cohorts
• How is timing of births influenced by education level?
• How is timing of births influenced by labour market conditions – specifically aggregate unemployment?
• Check sensitivity of results to unobserved heterogeneity
British Cohort Datasets
• National Child Development Study (NCDS)– women from a cohort born in a particular week in
March 1958– combine birth history data from 1991, 2000 and 2004
sweeps
• British Cohort Study (BCS70)– women from a cohort born in a particular week in April
1970– combine birth history data from 2000 and 2004
sweeps
Information available on the samples of women
N %
NCDS women (1958 cohort)Complete birth history to age 33 519 9.2
Complete birth history to age 42 840 14.9
Complete birth history to age 46 4,272 75.9
TOTAL 5,631 100.0
BCS women (1970 cohort)Complete birth history to age 29/30 892 17.5
Complete birth history to age 34 4,213 82.5
TOTAL 5,105 100.0
Proportion with first birth by age 25
05
101520253035404550
NCDS (1958 cohort) BCS (1970 cohort)
Education Levels
NCDS (born 1958)
Low
Medium
High
BCS (born 1970)
Low
Medium
High
Survival Curves for First Birth by Education Level
NCDS (1958 cohort) BCS (1970 cohort)
0
10
20
30
40
50
60
70
80
90
1stQtr
2ndQtr
3rdQtr
4thQtr
East
West
North
0.00
0.25
0.50
0.75
1.00
0 100 200 300 400Months since Age 16
Low MediumHigh
0.00
0.25
0.50
0.75
1.00
0 50 100 150 200 250Months since Age 16
Low MediumHigh
Claimant Count Unemployment Rate - Men
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
PE
R C
EN
T
original
adjusted
Method (1):
• Investigate time to first three births• Use hazard models (event history models)• education and lagged unemployment as
explanatory variables• Other variables in model include: age 11 ability
test scores, free school meals (age 11), Father’s SES, mother’s education, religion, number of siblings
Method (2): • Continuous time hazard model estimated in
CTM• Estimate:
where h is the hazard; t is duration in state i before exiting to state j; X is a vector of explanatory variables; θ is person-specific unobserved heterogeneity
• θij = fijθ • Use non-parametric specification of
heterogeneity
]exp[ 2210 ijij ijijijijijijij
fXtth
Results for EducationHazard model jointly estimated for first three births
First birth Second birthNCDS (1958 cohort). Education, base category = lowMedium -0.381
(0.046)
-1.175
(0.105)
0.027
(0.047)
-0.108
(0.055)
High -0.618
(0.059)
-1.999
(0.150)
0.117
(0.056)
0.059
(0.066)
BCS (1970 cohort). Education, base category = lowMedium -0.273
(0.040)
-0.442
(0.060)
-0.030
(0.051)
-0.088
(0.059)
High -0.695
(0.054)
-1.281
(0.077)
0.045
(0.065)
-0.115
(0.077)
Controls for heterogeneity No Yes No Yes
Control variables: all; heterogeneity controls non-parametric;
standard errors in parentheses
Results for UnemploymentHazard model jointly estimated for first three births
First birth Second birthNCDS (1958 cohort)
Lagged unemployment -0.012
(0.007)
-0.003
(0.008)
0.008
(0.005)
0.054
(0.007)
BCS (1970 cohort)
Lagged unemployment -0.043
(0.009)
-0.048
(0.009)
0.008
(0.007)
-0.032
(0.009)
Controls for heterogeneity No Yes No Yes
Control variables: all; heterogeneity controls non-parametric specification;
standard errors in parentheses
Results: Heterogeneity
• Allowing for unobserved heterogeneity:– Improvement in fit of models– Results for both education and unemployment
sensitive to the inclusion of heterogeneity terms
Conclusions
• Results consistent with interpretation of education as a causal influence on fertility (time to first birth)
• Results for aggregate unemployment: negative effect on 1st birth, significant only for 1970 cohort
• Important to control for unobserved heterogeneity in modelling times to first and higher order births
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