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