1. Social Polarisation in the timing of First Birth
Examining the truth behind the myth of the 'the Monstrous Army on the March'
Dylan Kneale & Heather Joshi
Institute of Education

2. Background I
Recognition that rates of transition to parenthood are decreasing - Men and women are postponing parenthood or avoiding parenthood altogether.
Known patterns of social polarisation in age at first birth. Early parenthood associated with a range of negative predictive characteristics and outcomes for parents and children.
Recent interest has focussed upon role of education in determining rates of transition to parenthood.
In particular, education differentials have been isolated as markers of increasing polarisation in age at first birth.
Recognition that rates of transition to parenthood are decreasing - Men and women are postponing parenthood or avoiding parenthood altogether.
Total fertility rate dropped from 2.77 in 1960 TO 1.87 in late However, this figure of 1.87 is the highest the TFR has been for 26 years.
At the same time the mean age at first birth rose among women from 27.4 in 1960 to 29.2 in Among men, 2/3 of all paternities (including higher parity births) in 2005 occurred among men aged over 30 years, although comparative data on the trends in age at first birth for men is rare.
Age at first birth associated with a number of characteristics.
Younger parents are associated as being more likely to be unmarried, lone parents with relatively poor rates of educational achievement and poor socioeconomic circumstances.
Older parents are associated with a range of more advantageous predictors.
The children of young parents are associated with a range of negative outcomes including higher rates of infant mortality, childhood accidents, poorer rates of educational achievement to name but a few. However, it is unclear whether early parenthood per se is the root cause of these negative outcomes or whether existing poverty is causal.
Recent interest has focussed upon education in determining transition to parenthood. Poor educational attainment has been linked to earlier parenthood through a variety of routes such as earlier intercourse, reduced career motivations and limited social networks – pathways that were recently summarised in a systematic review by Harden, Brunton et al (2006). Conversely, delaying parenthood and reduced levels of transition into parenthood have been associated with higher educational levels.
However, what has been apparent in the media recently is speculation that polarisation in the timing of birth is increasing between groups.

3. Background II
Recent media reports have suggested that women and work, and especially graduate careers, are becoming more incompatible with childbearing.
/*Read some of the headlines and the final sentence of Alison Wolf*/
Further cite speculation that this due to women choosing to have careers over children
Other possible contributory explanations; women who are en route for higher qualifications are better placed to avoid early parenthood
Conversely anyone who delays the decision may be beaten by the biological clock with the result of unintended childlessness
Other reasons for delaying may include generally uncertainty, waiting for the ‘right’ partner, waiting for a stable partnership, waiting for a joint decision which could be affected by the partner’s career, constraints on finding housing

4. Background & Aims
(Wolf): Graduate women = 'the Monstrous Army on the March'
What about graduate men – monstrous army still marching?
Focus has been on increasing polarisation and rising childlessness – but several different scenarios possible
In addition are differentials caused by different sample composition within groups, postponement or genuine decreased levels of transition?
Aims:
Explore polarisation within and between two birth cohorts
Examine the situation for males – increasing polarisation too?
Examine some of the determinants of fertility differentials
Graduate women have been described by some authors as a monstrous army on the march. According to some, these women represent a new wave who believe that the quality of life is best improved by putting yourself first. This is consistent with some of the doctrine of the Second Demographic transition. However, there is scant attention paid to the fertility habits of men – are graduate men also following these trends.
In addition, the headlines have focussed on increasing rates of polarisation between groups. This is one level of stratification of overall population estimates. However, does this crude stratification actually mask differences or similarities in fertility patterns. Furthermore, are these particular subgroups that exhibit divergent trends.
Additionally, numerous ways of estimating what could happen in the future but what assumptions do these estimates male. For example, 40% childless graduate women is overly pessimistic – how do different assumptions affect the estimated rates of childlessness.
Aims of this paper:
Explore levels of polarisation within and between two British birth cohorts and examine some of the truth behind the rising levels of childlessness
Extend this analysis to males and examine whether they too are predicted to live their lives childless. Although, while the reproductive capacity for males has no defined upper age limit, based on all births in 2005, those fathered by fathers aged 45 or over accounted for less that 4% of all births.
Examine some of the determinants of these increasing levels of polarisation and explore whether it is actually a change of composition within groups that accounts for the reported increases in polarisation.

5. Data I
Analysis will use data from two British Birth Cohorts – National Child Development Study (NCDS, 1958) and the British Cohort Survey (BCS70, 1970).
Both studies began as a census of all UK births in a week, with additions in childhood waves.
In total, data for 18,558 and 18,731 collected at some point for NCDS and BCS70 respectively.
Attrition has affected both studies, with sample sizes at the last wave of data collection totalling around 9,500 for both.
However, population estimates of fertility transition appear consistent with external data (for women)
We use data from the National Child Development study (NCDS) and British Cohort Survey (BCS70) for this analysis.
Both studies started as a census of UK births.
There were additions of immigrants into the childhood waves of both studies. Although both studies began as a census of all UK births, those resident in Northern Ireland were discontinued after the birth survey for BCS70.
In total data for over eighteen and a half thousand NCDS cohort members has been collected at some point and over 18,700 cohort members for BCS70 (including Northern Irish cases).
However, attrition has affected both studies, to a greater degree possibly for BCS70. However, despite this, data was collected for over 9,500 cohort members for both studies respectively.
In addition, fertility estimates appear to be remarkably consistent with those from external national statistics sources for women at least. Women appear to be experiencing comparable transition rates into parenthood by age – although this is based upon descriptive data for the estimated average number of liveborn children for women in England and Wales produced by the ONS. For the NCDS, they seem slightly more likely to have experienced first birth by the age 0f 45 at 84% compared with 82% for national statistics. For BCS70 there is a little more variation in fertility schedules with childlessness at 34 estimated at 73% for National Statistics estimated and 71% for BCS70 estimates. However, as the focus of this paper is not to estimate population level estimates of fertility, this is immaterial.

6. Data II 1965 NCDS (Age 7) 1974 NCDS (Age 16) 1991 NCDS (Age 33)
1958 NCDS Birth
1969 NCDS (Age 11)
1981 NCDS (Age 23)
2000 NCDS (Age 42)
This slide outlines the data collection points for NCDS and BCS70.
1975 BCS70 (Age 5)
1986 BCS70 (Age 16)
2000 BCS70 (Age 30)
2004 BCS70 (Age 34)
1970 BCS70 Birth
1980 BCS70 (Age 10)
1996 BCS70 (Age 26)

7. Changes in Sample Composition
Twelve year gap between cohorts has meant both were born into very different British societies (Wadsworth, Ferri et al. 2003). In particular, large changes in educational achievement.
Despite the gap of only twelve years between the cohorts, both grew into very different British societies.
These were characterised by changes in terms of increased female autonomy, family life and marriage patterns, changing work patterns, social attitudes and participation, health and numerous other fields related to sociological and technological advancement.
Of interest for this paper are the changes in educational achievement and social class. These proportions refer to the population for fertility data and refer to highest educational achievement by the age of 33 years for NCDS and 34 years for BCS70. Generally, highest qualification using these categories is achieved preceding parenthood, although for some it will have been gained after first parenthood. In addition, graduate level qualifications refer to both academic and vocational level qualifications – i.e. NVQ Level 4 and above. While the timing of the qualification may be problematic to some extent in not being predictive, to some extent the approach is simply to compare graduate populations. This approach is a rough approximation –it assumes those who were going to become ‘graduates by max age would mostly have been aware that they were headed for his outcome while childless, and equally arbitrarily ignores those few people in NCDS who improved their qualifications after 33, whether before of after becoming a parent.
While there was a noticeable shift in patterns of educational achievement; in terms of social class, there was less movement. Social class categories stayed relatively constant in number between the cohorts. In addition, there was little difference in terms of the composition of social class and educational achievement – i.e. the graduate population was composed of similar populations in terms of social class in both cohorts – with the proportion of graduates who were from the highest social class standing at 11% and 12% for NCDS and BCS70 respectively; and from the lowest social class standing at 2% and 3% respectively for NCDS and BCS70. This is consistent with the overall population, as outlined by Makepeace et al 2003.

8. Entry into parenthood: Overall cohort populations
Gender ♂ ♀
Cohort
NCDS
(N = 7,142)
BCS70
(N = 5,862)
(N = 7,034)
(N = 6,062)
Parents at Age 20 years
3.9%
3.2%
12.8%
10.1%
Parents at Age 25 years
28.2%
16.6%
41.4%
29.7%
Similar proportions of early parents exist in both cohorts. Differences open up in early and mid twenties so that by 34 years:
So, for the overall population with fertility data, there exist over 14,100 cases for NCDS and almost 12,000 cases for BCS70. These populations are reduced when further stratification by covariates takes place.
From this table, the clear gender split is evidence with men entering into parenthood later than women as all three sample points featured. What is also clear is that the rates of teenage parenthood between the cohorts are overall comparable. However, the real delay comes in the mid to late twenties so that by the age of 34 years, there exists a 9% reduction in the proportion who had entered motherhood and a larger 15% reduction in the proportion of fathers by the age of 34 years.
Most of the discourse in population level fertility decline has concentrated on the fact that the population is now a more highly educated population, which in turn leads to a reduced fertility rate. However, the articles presented earlier actually go further and state that within groups, there are inflated levels of postponement and fertility decline over time – and that these differences between groups are actually increasing.
Parents at Age 34 years
68.0%
53.2%
77.9%
68.9%

9. Highest educational level as a marker of polarisation
Qualifications at age 33/34 years ♂ ♀
Tertiary Level
NCDS
(N = 1,727)
BCS70
(N = 2,108)
(N = 1,550)
(N = 2,301)
Parents at Age 22 years
2.8%
2.0%
1.7%
7.3%
Parents at Age 34 years
61.4%
44.2%
64.6%
57.7%
Intermediate
(N = 3,261)
(N = 2,511)
(N = 3,459)
(N = 2,716)
10.6%
8.0%
23.0%
20.8%
69.9%
57.2%
80.6%
75.6%
None
(N = 686)
(N = 285)
(N = 824)
(N = 245)
21.4%
15.1%
50.1%
52.7%
71.7%
60.4%
88.0%
81.3%
Certainly this table show an existing level of social polarisation in transition to parenthood by the age of 34 years. Cohort members with tertiary level qualifications can be observed to experience the slowest rates of transition to parenthood of any group.
There are also a number of other features of note in this table.
A larger proportion of tertiary qualified cohort members were teenage mothers in the BCS70 cohort. On these cases, childbirth almost certainly preceded obtaining the tertiary qualification, and is likely to be evidence of a wider culture of life long learning to which the latter cohort were exposed to.
Rates of teenage parenthood remained constant between cohorts with two exceptions – graduate women and men with no qualifications.
For the NCDS cohort there was a relative equal share of parents split by gender amongst tertiary qualified cohort members – by the BCS70 cohort, large gender differentials had opened up.
In fact, compared with their predecessors BCS70 men are substantially less likely to have entered fatherhood than NCDS. The highest drop between cohorts for any education subcategory was a 17% drop in rates of fatherhood by the age of 34 years for tertiary qualified males. This compared with reductions of between 5-7% in the rates of motherhood at age 34 years for all female education groups.
However, while there are between cohort changes in rates of parenthood, the actual differential between education categories within cohorts, a measure of increasing or decreasing polarisation appear relatively stable. The exception to this being the difference between tertiary qualified males and males with intermediate qualifications at age 34 years. In the 1958 cohort, at age 34 years for every 100 males with intermediate qualifications who were fathers there were 88 with tertiary level qualifications. By 1970 this had dropped to 77 males with tertiary qualifications.

10. Predicting future trends
Numerous different approaches for predicting future trends based on existing levels of polarisation. Five approaches used in the next part:
NCDS parenthood
Postponed NCDS parenthood
Flight from parenthood
Covariate specific flight from parenthood
Covariate specific postponed flight from parenthood (!)
….and bringing in intentions later.
Numerous methods for predicting future trends. The five used in the paper are outlined below – but you shouldn’t take too much notice of the title of these methods. Just trying to use shorthand to say:
Assumption 1: Assume BCS70 will experience NCDS age specific hazards of entering parenthood
Assumption 2: Assumed that BCS70 will experience NCDS age specific hazards from an earlier age – i.e. assume that BCS70 are equivalent in fertility behaviour to NCDS cohort members of a younger age.
Assumption 3: Examine the differential in the hazard of entering parenthood – i.e. use cohort as a covariate within a Cox’s regression model (when the proportional hazards assumption is not violated) and assume that this decreased entry into parenthood will remain constant and apply to NCDS hazard rates.
Assumption 4: Assume that there is the cohort effect, but control for other childhood and teenage covariates that may influence the cohort effect – i.e. add in covariates to control for the effect of cohort.
Assumption 5: Assume that the BCS70 cohort members are equivalent to NCDS cohort members at a certain age, but that they are also subject to a cohort effect. Theoretically, both may cancel each other out, but empirically they don’t. Basically saying that there is postponement, but that there is also a lower propensity to enter parenthood.

11. Results I: Tertiary Qualified Women
At age 45, 23% of NCDS tertiary qualified women remained childless. Estimating a postponement effect for BCS70 allows for the most generous estimate of entry into motherhood while the estimate for flight from parenthood estimates the most pessimistic estimate – i.e. that decreased rates of entry into motherhood observed among BCS70 women will continue – i.e. there is no postponement effect. This estimates that just over a third of women will be childless by the age of 45, probably childless for life. This most conservative estimate of entry into motherhood is that which was reported within the newspapers – and even this is below the 40% reported in some publications.
Another point of note is that all estimates are approximately within 10% of each other.

12. Results II: Tertiary Qualified Men
For males, the estimated rate of childlessness at age 45 is above that for women in almost every scenario bar that of postponed NCDS parenthood rates. Among the NCDS cohort, by the age of 45 years, tertiary qualified men have a slight advantage above graduate women in terms of entry to parenthood – this is not generally replicated among these scenarios.
Childlessness at 45 years reaches up to 40% in the most pessimistic estimate where postponement is not considered. However, as mentioned earlier, given that there is no set upper limit on reproductive capacity for men, childlessness at 45 years may not necessarily equate to lifetime childlessness.

13. Results III: Intermediate and No Qualifications
Cohort and Projection Method
Intermediate Qualifications
No Qualifications ♂ ♀
Childless at 45
NCDS
20.5%
13.9%
24.3%
10.5%
BCS70 – NCDS Parenthood Rates
29.8%
18.0%
32.0%
16.7%
BCS70 – Postponed NCDS Parenthood Rates
21.7%
13.5%
24.1%
11.0%
BCS70 – Flight from Parenthood
35.0%
19.7%
33.9%
17.6%
BCS70 – Covariate Specific Flight from Parenthood
19.6%
34.3%
17.7%
BCS70 – Covariate Specific Postponed Flight from Parenthood
28.5%
15.5%
27.9%
13.1%
In comparison to women, NCDS men with intermediate and no qualifications pay a penalty in comparison to their tertiary qualified counterparts. NCDS tertiary qualified men have slightly higher rates of transition to parenthood than tertiary qualified women, although this picture reverses for those with intermediate and no qualifications.
For men with intermediate qualifications for those with intermediate qualifications, childlessness estimates stand at between 22-35% while those for men with no qualifications stand at between 24-34%. There is definitely some sort of penalty for males no having any qualifications – which may not be completely a surprise.
For women, estimates of childlessness at age 45 generally vary between % for those with intermediate qualifications and 11-18% for those with no qualifications.

14. Increasing rates of polarisation?
Distinctive patterns of parenthood based on educational achievement in both cohorts.
For women, relative proportions entering motherhood by highest qualification level expected to stay constant – childlessness expected to rise gradually among all groups.
For men, gap in fatherhood rates between education levels is projected to change in some scenarios.
Gap between tertiary qualified and males with no and intermediate qualifications could widen–myth of monstrous women replaced by monstrous male graduates?
Gap between males with no and intermediate qualifications could narrow.
The results show that there are distinctive patterns of parenthood between educational levels, and that these patterns are expected to remain to a certain extent in both cohorts. For women, a linear trend in terms of childlessness is expected to continue, whereby Tertiary qualified women are expected to have the highest rates of childlessness, followed by those with intermediate qualification with those with no qualifications expected to have the highest rates of motherhood.
Among NCDS men, those with no qualifications have the highest rates of childlessness, followed by those with tertiary qualification followed by those with intermediate qualifications. In some scenarios, this trend changes and begins to follow a linear trend similar to that of women, whereby tertiary level qualified have the highest rates of childlessness and those with no qualifications the lowest. Generally, in terms of polarisation, the gap between tertiary qualified males and intermediate is expected to widen; as is that between tertiary and no qualifications. For example, among NCDS men, for every 100 childless tertiary qualified men there were 89 with no qualifications. For BCS70 males, the trend becomes less clear, with for every 100 childless tertiary qualified men, between 90 and 124 men with no qualifications are expected. However, the gap between those with intermediate qualifications and no qualifications is expected to narrow. This suggests that for males at least, there is increasing polarisation in terms of transition to parenthood, and certainly age at first parenthood.

15. Tertiary Qualified I: Vocational Vs Academic
Cohort and Projection Method ♂ ♀
Childless at 45 -
Academic
Vocational
NCDS
24.8%
17.1%
26.7%
19.1%
BCS70 – NCDS Parenthood Rates
28.2%
23.6%
27.8%
20.3%
BCS70 – Postponed NCDS Parenthood Rates
25.6%
22.3%
26.5%
17.5%
BCS70 – Flight from Parenthood
37.1%*
32.9%**
30.5%***
22.4%***
BCS70 – Covariate Specific Flight from Parenthood
37.3%*
31.0%**
****
BCS70 – Covariate Specific Postponed Flight from Parenthood
35.0%*
25.7%**
29.3%¹
19.8%¹
*Using observation time; **Using observation time; ***Using observation time; **** Cohort effect drops out of significance when introducing other covariates; ¹Unadjusted cohort effect is used;
So far, tertiary qualified cohort members have been treated as homogenous populations between cohorts. However, within these populations, there may be characteristics differences that are masking some of the trends described earlier in transition to parenthood and age at first birth. In particular, the ratio of academically and vocationally qualified cohort members within the cohort, and their differential fertility patterns, may actually mask some of the divergences or similarities between cohorts.
When the tertiary qualified is split differences for men but particularly women are attenuated. Projecting these results shows that there is little projected difference in rates of childlessness for female holders of tertiary qualifications, although for males the picture is quite different. Male rates of childlessness at the age of 45 years for the 1970 cohort compared with the 1958 cohort are estimated to lie between 0.8%-12.5% and 5.2%-15.8% higher for holders of academic and vocational tertiary qualifications respectively.
In a sense, for females, the differences that were observed earlier were largely caused by differences in sample composition, with a larger proportion of the BCS70 tertiary qualification holders being degree holders. Differences have attenuated to the degree that cohort is actually not a significant predictor of entry into parenthood in the presence of other covariates, hence the absence of estimates for the covariate specific flight from parenthood.
For males, there is evidence of a difference that may be caused by other, unobserved differences in sample composition or by actual fall in parenthood transition rates and postponement.

16. Tertiary Qualified II: Subject of qualification
Childlessness at 34; results for academic graduates
In addition to differences in the type of tertiary qualification held being instruments in determining patterns of transition to parenthood, subject of qualification is also instrumental.
For male graduates, at age 34 there are large increases in the childless BCS70 population compared to NCDS in all subjects with the exception of other miscellaneous vocational qualifications – these include those holding qualifications in Hospitality, Catering, Retail and Land Management; where the proportion of those childless at age 34 years was estimated to be 4% lower than NCDS, although this difference was not significant.
For women in the NCDS cohort, those with Social Science degrees were more likely to be childless with those with other subject types having lower rates of childlessness. This is also consistent with other studies, such as that of Hoem in Sweden, and in this cohort we attribute this effect to Science and Maths and Education and Humanities graduates entering child friendly teaching roles, with Social Sciences entering roles outside education. By the BCS70 cohort this pattern has attenuated and it is now those in Education, Humanities and Creative Arts who are most likely to be childless at age 34 years.

17. Measuring Postponement and Infertility
Information on intentions to bear children and infertility of cohort member and/or partner collected in both cohorts.
This information gives the first indications that BCS70 cohort is postponing as opposed to avoiding parenthood.

18. Results IV: The impact of postponement – Tertiary Qualified Males

19. Results V: The impact of postponement – Tertiary Qualified Females

20. Conclusions I Social Polarisation is evident in age at first birth.
Higher education levels obtained are correlated with later transition to parenthood.
Delay appears to have affected males with tertiary qualifications disproportionately.
Populations stratified by education level are not homogeneous between cohorts.
Partial estimates that do not fully take postponement and infertility into account predict higher rates of childlessness for all populations stratified by education level.

21. Conclusions II
When postponement and infertility are factored in, projected childlessness could actually drop. Polarisation remains in age of transition although attenuated for final transition rates.
However, this could well be offset by higher rates of unintended childlessness.
Mirowsky (2005) suggests 34 years to be the optimum age for childbearing taking into account socioeconomic and biological factors.
In terms of intentions at least, little truth in ‘monstrous army on the march’ for women (or men).
Future Work:
Project flight from parenthood scenario using infertility and postponement information

22.
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