The Relationship between Childbearing and Transitions from

Marriage and Cohabitation in Britain

Fiona Steele1, Constantinos Kallis2, Harvey Goldstein1 and Heather Joshi3

1University of Bristol,2LSHTM, 3Institute of Education

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Research Questions

• What is the link between partnership (marriage or cohabitation) stability and childbearing?– Allow for joint determination of partnership

and fertility processes– Consider effects of presence and

characteristics of children and pregnancy

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Key Findings from Previous Research

• Having children together lowers the risk of dissolution for married couples, but there is little evidence of an effect among cohabitees

• Among cohabitees, having children is associated with decreased odds of marriage in GB and Canada, but increased odds in US (Manning & Smock). Sharp increase in odds of marriage during pregnancy

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Endogeneity of Prior Fertility Outcomes

• Interested in effect of presence of children on partnership transitions. But children are prior outcomes of a potentially correlated process (fertility).

• There may be factors (some unobserved) which influence decisions about partnership transitions and childbearing. If ignored, estimates of effects of interest will be biased.

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Methodology used in Previous British Studies

• Most consider 1st partnership only– Those using NCDS look at transitions for ages 16-33

(e.g. Kiernan & Cherlin 1999; Berrington 2001)

• Transitions from marriage and (unmarried) cohabitation usually modelled separately

• Prior fertility outcomes usually treated as exogenous

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Our Methodological Approach

• Consider all partnerships for ages 16-42 using multilevel modelling

• Estimate simultaneously models for 3 types of partnership transition:– Marriage Separation– Cohabitation Separation; Cohabitation Marriage

• Estimate these transitions jointly with model for fertility to allow for potential endogeneity of fertility outcomes

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Joint Modelling of Partnership Transitions and Fertility

• Our research builds on US study (Lillard & Waite 1993) which used a multiprocess model to allow for possibility that the processes of divorce and childbearing are jointly determined– BUT only marital unions were considered

• We extend their approach to include outcomes of cohabiting partnerships

• Another British study (Aassve et al. 2006) also models union dissolution and fertility jointly, but groups together marriage and cohabitation. Recent US studies combine cohabitation and single

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Methodology: Overview• Multilevel data structure: repeated partnerships and

births (level 1) within individuals (level 2).

• Use multilevel multistate discrete-time event history model (Steele et al. 2004) for partnership transitions.– ‘States’ are marriage and cohabitation– Competing risks from cohabiting state

• Estimate jointly with model for conceptions within partnerships using simultaneous equation (multiprocess) model (extending Lillard (1993) who considers only marriage).

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Multilevel Modelling

• Some women have > 1 partnership and/or conception– May be unobserved characteristics which influence risk of all

partnership transitions/births – Leading to correlation between durations of partnerships/birth

intervals for the same woman

• In a multilevel model, include random effects for each type of transition. These represent unobserved time-constant variables

• Correlation between random effects for different transitions are of substantive interest

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Multiprocess Model of Partnership Transitions and Fertility

Probability of partnership transition at time t

Probability of conception at time t

Children conceived before t

XP(t)

(Observed)

XF(t)

(Observed)

uF

(Unobserved)

uP

(Unobserved)

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Data

• 1958 British birth cohort (National Child Development Study):– Partnership (living together for >1 month) and birth

histories collected retrospectively at ages 33 and 42. Linked to form history for age 16-42.

– Covariates from childhood and adulthood.

• Analysis sample: n=5142 women with 1 partner by age 42; n=7032 partnerships and n=9137 “partnership episodes”.

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Measures of Prior Fertility(All Time-Varying)

• Current pregnancy status

• Number of preschool and older children living with respondent

• Distinguish between children fathered by current and previous co-resident partners, and those from non co-resident relationships

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Other Explanatory Variables

• Previously married/cohabited• Age at start of partnership• Partnership duration• No. years of education (time-varying)• Paternal social class• Family disruption before age 16• Region of residence at birth• Housing tenure at birth

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Years to Partnership Transition: Quartiles

25% 50% 75%

Marriage Separation

12.0 - -

Cohab Separation

3.5 8.3 -

Cohab Marriage

1.3 2.9 8.8

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Cross-Process Residual Correlations (* denotes significance at 5% level)

• Separation from marriage and marital conceptionr = -0.07 (-0.28* before accounting for current pregnancy)

• Separation from marriage and cohabiting conceptionr = 0.42*

• Separation from cohabitation and cohabiting conceptionr = 0.32*

• Cohabitation to marriage and cohabiting conceptionr = 0.30* (0.43* before accounting for current pregnancy)

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Effects of Fertility Variables on Log-odds of Marital Separation

Age/Father Single Process

Multiprocess

Currently pregnant -1.42* -1.41* Preschool/Current 1 -0.51* -0.51* 2+ -1.00* -0.99* Older/Current 1 -0.33* -0.34* 2+ -0.67* -0.70* Preschool/Previous 0.24 0.21 Older/Previous 0.06 0.05 Non-coresident partner 0.61* 0.58* *significant at 5% level

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Effects of Fertility Variables on Log-odds of Separation vs. Staying Cohabiting

Age/Father Single Process

Multiprocess

Currently pregnant -0.64* -0.70* Preschool/Current 1 -0.24* -0.29* 2+ -0.75* -0.88* Older/Current 1 -0.03 -0.06 2+ 0.24 0.14 Preschool/Previous -0.33 -0.33 Older/Previous -0.01 -0.02 Non-coresident partner -0.02 -0.02 *significant at 5% level

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Effects of Fertility Variables on Log-odds of Marriage vs. Staying Cohabiting

Age/Father Single Process

Multiprocess

Currently pregnant 0.69* 0.65* Preschool/Current 1 -0.19* -0.22* 2+ -0.08 -0.14 Older/Current 1 -0.35* -0.37* 2+ -0.28 -0.35 Preschool/Previous -0.06 -0.07 Older/Previous -0.03 -0.03 Non-coresident partner -0.41* -0.42* *significant at 5% level

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Further Work Under Research Methods Project

• Comparison of effects of having children on cohabitation outcomes for 1958 and 1970 birth cohorts

• Effect of having children on partnership formation and outcomes for 1970 cohort

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Cohort Comparisons for Cohabitation Outcomes(1958 and 1970 cohorts, age 16-30)

• Sharp fall in proportion ‘legalising’ cohabitation during pregnancy

• In 1970 cohort only, evidence of stabilising effect of having children together (lower risk of dissolution)

• But having school-age child from previous partnership reduces odds of marriage in 1970 cohort

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Effects of Fertility on Partnership Formation(1970 cohort, age 16-30)

• Pregnancy hastens cohabitation and marriage among single women

• Presence of preschool child from previous partnership inhibits cohabitation among single women

• Presence of a school-age child from previous partnership inhibits marriage (among both single and cohabiting women)

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Publications

Steele, F., Kallis, C., Goldstein, H. and Joshi, H. (2005) “The Relationship between Childbearing and Transitions from Marriage and Cohabitation in Britain”, Demography, 42: 647-673.

Steele, F., Joshi, H., Kallis, C. and Goldstein, H. (2006) “Changing Compatibility of Cohabitation and Childbearing between Young British Women born in 1958 and 1970”, Population Studies 60(2): 137-152.

Steele, F., Kallis, C. and Joshi, H. (2006) “The Formation and Outcomes of Cohabiting and Marital Partnerships in Early Adulthood: The Role of Previous Partnership Experience”, Journal of the Royal Statistical Society, Series A 169(4): 757-779.