What explains the change in the number of children women have?
Women's empowerment, the increasing well-being and status of children, technological and economic changes, changing norms, and opportunities for family planning matter for the reduction of the total fertility rate that I documented above. Below I will review both the theoretical explanations of how each of these aspects impacted the number of children women have and also present the empirical research that investigates these explanations.
What makes precise accounting difficult is that the different explanations of declining fertility are not mutually exclusive. But my sense from reading the literature is that over the long-run the two first explanations – women's empowerment and the increasing well-being and status of children – have been the two most important factors in most places.
Empowerment of women
Women's Education
The level of education in a society – of women in particular – is one of the most important predictors for the number of children families have. Before I am looking at the data and the empirical evidence in the research literature that establishes why increasing education is leading to a declining number of children per woman we should ask why and how exactly women's education is linked to the choice about children. We should look at the theory.
Positive feedback via the health of children
There is evidence, which we discuss
in our entry on child mortality, that better education of mothers is having a positive impact on better health and lower mortality of the children. Further below I will review the evidence that lower child in turn leads to a decrease of the total fertility rate. Taken together these two pieces of evidence suggest that better education of women reinforces the direct effect it has on fertility through an additional indirect effect via better child health.
Positive feedback via contraceptives
Education is also important for the knowledge and use of contraceptives and the ability of better educated women to reduce the gap between the desired and the actual number of children is an additional positive feedback effect by which better education reduces the number of children. Chicoine (2012) finds evidence for the importance of education in this regard.
Positive feedback via lower fertility
The shortest loop of positive feedback runs through fertility itself. Education is not only reducing fertility, lower fertility also allows for better education. Better education of women thereby reinforces itself, both within as well as across generations.
Evidence for this two-way reinforcing relationship can be found in the historical transition to lower fertility in Prussia which was studied by Becker, Cinnirella and Woessmann (2010).
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The effect that better education has on lower fertility can reinforce itself also over subsequent generations. As the fertility rate declines the education system faces smaller and smaller cohorts of school children for which it can better provide. And additionally parents with fewer children also have more opportunities to nurture and support each child. This is a kind of demographic dividend on education.
Better education makes it possible for social norms to change
In both historical and contemporary episodes of declining fertility researchers have found strong evidence that social norms are important in reducing the number of children that parents desire – I will present some of this evidence below. Education seems to be a key prerequisite for these changes to take hold.
Women’s Labor Force Participation
The increasing labor force participation of women is a second aspect of women's rising empowerment in society and this change too tends to lead to a decline of the number of children that women have. This change is so closely linked to the rising education of women discussed before that it is indeed impossible to separate from that. A substantial part of the increased opportunities that better education offered were realized in the labor market and it can be argued that the best way to understand how education matters for fertility rates is to view it together with women's increasing labor force participation.
Increasing well being and status of children
Child mortality
Rapid population growth has been a temporary phenomenon in countries around the world. Rapid population growth starts when the health of the population improves and the mortality rate in a population decreases while the birth rate stays as high as before. Rapid population growth then comes to an end when after some time the birth rate follows the decline of the mortality rate. The model of the demographic transition formalizes this relationship between mortality, fertility, and population growth. Is the regularity of this co-movement of mortality and fertility rates just a coincidence?
The theoretical and empirical literature suggests that these changes regularly coincide with additional changes – such as those discussed above – and that the link is therefore partly driven by changes of third factors. But the literature additionally suggests that there is a important direct and causal effect of declining mortality – particularly of children – on the number of children parents are having. The sections below discuss first the theoretical reasoning and then the empirical evidence.
In an environment with high child mortality women will give birth to more children than they want to ensure against the loss of children
The theoretical argument for the link between high mortality – particularly at a young age – and families' decisions for a certain number of births becomes understandable when one considers how families who want a certain number of children are forced to think in a high mortality environment. If parents have a certain target for a number of surviving children then the number of children the women gives birth to will need to be higher when the level of child mortality is higher.
17 Two mechanisms are at work – none of which have a particular pleasant name in the demographic literature:
18
- "Child replacement": Parents that experience the death of a child might deliberately decide for an additional birth in order to “replace” a child that has died.
- "Child hoarding": Demographers speak of hoarding when a family decides to have more births than their desired number of children in order to protect themselves against the possibility of future high mortality in the family. The motivation for ‘hoarding’ is best understood in contrast to the motivation for replacement. Replacement is the response to the experience of a child death while hoarding is the response to the expectation of child mortality. This thinking becomes understandable when one considers that in pre-modern societies more than one third of all children die before they are five years old.
Of these two effects only hoarding can explain why a decline of fertility
follows a decline of child mortality in the way it is described by the model of the demographic transition. As child mortality decreases, parents gradually learn that the risk of child death is decrease and see that hoarding is not needed anymore. Finally in the absence of child mortality parents can decide directly the number of children that they want. Consistent with the model of the demographic transition there might be a time lag between declining mortality and declining fertility as parents will only in retrospect learn that the environment has changed and the risk of child death is declining.
More education for children made having children more expensive
In today's rich economies children have vastly more education than in the poor agrarian economies of the past. The basic argument for why the increase of education contributed to the decline of fertility rates derives again from the seminal work of Becker (1960) who argued that because of the costs of bringing up a child parents have to make a decision between the number of children they want (quantity) and the resources they want to spend on each child (quality). Limited resource force parents to decide to either have many children – but then have few resources (time & money) available for each child – or to have fewer children and then to be able to have more resources available for each child. This tradeoff is described in the literature as parents' choice between the "quantity" or the "quality" of their children.
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The argument in a nutshell is that educating children is very costly and since parents have limited resources the increasing costs of having children forced them to have fewer children.
Lower child mortality increases the incentives to invest more resources into children
A first extension of the argument linking fertility rates and children's education explains that this association is partly driven by the decline of child mortality. The model developed by Soares (2005),
27 argues that declining child mortality changes parents incentive in the quantity-quality-tradeoff described above. In the high mortality environment of the past, investments in the education of children had low returns since there was a high risk that the child does not survive. Parents therefore did not want to spend resources in educating children who are at a high risk of premature death and therefore might not benefit from that education. With little incentive into the uncertain future of their children, parents instead hoped to maximize the contribution from children to the household by increasing the quantity of children.
Falling child mortality then changed the incentives of the quantity-quality-tradeoff: The reductions in mortality – of children in particular, but over the life course more generally – increased the incentive for parents to invest in the education of their children (‘quality’) and with limited resources to spend on education they are thereby compelled to give up the goal of maximizing the number of children (‘quantity’). Lower child mortality increases the incentives to invest more resources into each child and with limited resources parents therefore chose to have fewer children
Technological and structural change increased the importance of education
Falling mortality of children is of course not the only reason why children in societies with better living conditions are better educated.
Technological change killed many of the low-skill, routine tasks that kept our ancestors busy and meant that workers in a modern economy need a much higher level of education. The economic change driven by technological improvements meant that the returns to education increased and these in turn increased the incentives to invest in the education rather than the number of children, as Becker, Murphy, and Tamura (1990) argue.
28 This tilted the quantity-quality tradeoff yet further away from a high number of children.
Children providing for their parents at an old age
In popular accounts, it is often argued that in the past and in poor economies parents aim for a large number of children as they will depend on them for support in old age. This argument cannot have played a large role before the onset of the demographic transition as the stagnation of population growth implies that on average only two children will reach the reproductive age.
But even for the time thereafter and more generally there is surprisingly little evidence for this argument given how well it is known. In reviewing the literature Bloom and Luca (2016)
31 conclude that “the empirical evidence supporting this hypothesis is surprisingly scarce.”
In a study in Indonesia Cameron and Cobb-Clark (2001)
32 find only very limited importance of the transfers of children to their parents and emphasize that instead the elderly are mostly relying on their own labor income even at an old age.
During the period of the demographic transition when mortality was low and fertility high however there is some evidence for the importance of children for old-age support from the US where Sundstrom and David (1988)
33 documented the importance of children for the old-age support of the parents before the civil war.
Also Billari and Galasso (2009)
34 examine the effect of a pension reform in the 1990s in Italy and find evidence that pensions and children are to some extent substitutes when it comes to support in old age.
Overall however the demand for children arising out of a need for support in old age is likely to be less important than other factors examined here.
Increasing prosperity and structural transformation of the economy
The following plot shows the close relation between the income level (measured by GDP per capita) and the total fertility rate. Shown are not just country averages of the fertility rate and income, the visualization is also showing the within-country inequality. Each population is split into 5 quintiles, from the poorest 20% to the richest 20%. Unfortunately there is no data available to do this perfectly and I had to combine income and wealth data to approximate the relationship: The fertility rate by the wealth quintile in each country is plotted against the respective income quintile in each country. The match is imperfect because I am assuming that each household is in the same income and wealth quintile and this is only an approximation of reality.
The reflex of many economists when thinking about the fertility rate is to point to income as the likely determinant. And sure enough, between countries and over time we see that higher incomes are associated with lower fertility. But good things come together – richer countries are also healthier and better educated – and so this correlation between high incomes and low fertility alone is surely not evidence that it is increasing income that is responsible for the decrease in fertility.
In fact we have already explored several third factors. Most obviously, a higher level of education of a population is a factor that contributes to higher prosperity and a lower number of children. And a second set of changes – technological change, lower child labour, and the structural change of the economy – comes along with economic growth and lowers the demand of parents for children, as we have seen.
But still there might also be a direct effect of increasing prosperity on the declining demand for children. Higher incomes make different, more varied lifestyles possible, which might convince prospective parents to have fewer or no children. With respect to the increasing prosperity in Europe over the last century the historians George Alter and Gregory Clark write:
35 “New products and new lifestyles in the growing metropolitan societies created by the Industrial Revolution expanded choices. Wealthy families responded by consuming more of these new products and services instead of producing children.”
The correlation that we see in the visualization below is therefore partly driven by a direct link between income and the number of children parents want, but to a large extent also by changes that correlate with prosperity and fertility rates.
Culture and norms
The change of fertility are a prime example for changing social norms. In many places around the world the practice of having more than 5, 6, 7, or 8 children, which was the norm for millennia, was replaced by the norm of having 2 children or fewer.
Earliest date of a 10% decrease in fertility in Europe42
Religion and fertility
Many religious teachings are asking the believers to have a large number of children. The Christian bible for example teaches to “be fruitful and multiply and fill the earth and subdue it”.
43
The visualization below shows the children per woman plotted against the share of children that die in the first 5 years of life. Each country here is colored according to the largest religious group in that country. The obvious relationship here is that in countries where more children survive, fertility is lower. Which religion dominates in a country has no clear relation to the fertility level – and even if does have some importance the correlation is much weaker than that with the health of children. Countries with a majority Christian population have fertility rates as high as 6 (DR Congo) and as low as 1.25 (Portugal) children per woman. Across countries fertility rates vary within and not between religions.
And what is true between countries is even more obvious for the change over time. Religious background cannot explain the rapid change in the level of fertility that we saw. Explanations that refer to the cultural background of a population regularly run into this problem that they can hardly explain the very fast socio-economic changes over time. Despite the ascribed values of a particular religion we have seen changes that are at odds with these: In catholic Italy the fertility declined from 2.5 in 1966 to 1.2 at its lowest rate in 1997, and in Muslim Iran the fertility declined from 6.5 children per woman in 1982 to 1.8 in 2005!
As it is so often the case with explanations for social phenomena, the importance of culture is easily overestimated.
While the big differences between countries today and changes over time are not determined by religion it would be wrong to say that religion has no importance for the number of children women have.
44 There is evidence that, everything else being equal, religious people have more children, so that religion matters for differences at the same socio-economic level. Still, the differences between religions within the same country are much smaller than the differences between different countries in different socio-economic conditions. We can see how much more living conditions matter than the religion.
And then there have been some small highly religious sub-populations in which religious teaching had a very substantial effect on fertility rates. The highest total fertility rate that I found for any population in human history was for the Hutterites –
a group of Christians with origins in Tyrol – where, in the early twentieth century, married Hutterite women in North America had on average 10.4 children.
45
Family planning
Family planning refers to all active efforts to chose actively the number of children a woman or family wants. While the changes discussed before changed the incentives for having a larger or smaller number of children, family planning is focussed on the decision making and implementation of that decision on the personal level.
Family planning involves the use of contraception as well as counseling by experts.
Why family planning is highly important today is to consider the share of pregnancies that are unwanted. The number of pregnancies that are unintended is very high. For the year 2012 – the last year for which we have data – it is estimated
46 that 85 million pregnancies were unwanted. These are 40 percent of all 213 million pregnancies in that year.
Of these 85 million pregnancies 50 percent ended in abortion, 13 percent ended in miscarriage, and 38 percent resulted in an unplanned birth. This means that 32 million children are born unplanned every year.
Contraception
Women’s empowerment and the increased status of children reduce the number of children that parents want. But a goal of lower fertility is irrelevant if there are no means to achieve it. Methods of contraception give parents the chance to get the actual fertility closer to their desired fertility.
Today there is a range of methods of contraception available which are referred to as "modern methods":
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- oral hormonal pills,
- the intra-uterine device (IUD),
- the male condom,
- injectables,
- the implant (including Norplant),
- vaginal barrier methods,
- female and male sterilization,
- the female condom
- and emergency contraception.
Coercive policy interventions
Did China's one-child policy reduce fertility?
A common claim—and one originated by the Chinese Government—is that China’s one-child policy has prevented approximately 400 million Chinese births. The view of many has been that this policy shaped a population age structure that contributed to economic growth (through the effect of the “
demographic dividend”) and even contributed to global efforts to address climate change. But was the policy necessary to drive down fertility?
But is it really? The chart shows fertility in China since 1945. The striking decline and rebound of fertility around 1960 is due to the Great Leap Forward famine. But otherwise fertility in China was over 5 and even as high as 7 children per woman in the 1950s and 60s. Then, fertility started to decline – and as we see from the chart this decline started in 1970, long before the introduction of the one-child-policy. China promoted family planning policy in the 1960s and 70s, but the one-child policy was phased in between 1978 and 1980. By the time of the introduction of the one-child-policy, fertility in China had already more than halved. The huge reduction in fertility happened irrespective of the one-child-policy. Until 1980 child mortality – which we saw is an important determinant of fertility – had already
halved from 12% (in 1969) to 6%.
In 2013 the researchers Wang Feng, Yong Cai, and Baochang Gu examined what China’s fertility rate would have been in the absence of the one-child policy.
53 Using data from countries that had a similar birth rate to China’s in 1970, they compared the trajectories of change in those countries with that of China. The study found that “in other countries without a one-child policy the birth rate also declined, and it declined below the level predicted for China.” Additionally, the researchers estimated what China’s fertility would have been without the one-child policy by using the UN’s 2011 population projection model. The results showed that China’s fertility rate, which was already on a rapid decline in 1970, would have continued to decline after 1980 and by 2010 “fertility would have fallen to its currently observed level.” The continuation of the decline is due to the continuations of improving living conditions in China over this period.
Also shown in the chart is the evolution of fertility in Taiwan. Taiwan – which is claimed by China as part of China – never introduced a one-child-policy. Yet, Taiwan experienced the same decline that China did. From around 7 children per woman to fewer than two. Today the fertility in Taiwan is even lower than in China. In fact the fertility is close to 1 child per woman – just the aim that China had and never reached despite this being the planned outcome of the Chinese government. The point here is that economic and social development is truly important and ultimately what influences women’s decision about how many children they want to have.
Did the one-child-policy work? Fertility in China and Taiwan (1945-2015)
Fertility is first falling with development – and then rising with development
We have already seen that as a country develops – child mortality declines and incomes grow – the fertility declines rapidly.
The demographers Mikko Myrskylä, Hans-Peter Kohler & Francesco Billari studied what happens at very high levels of development. To measure development they relied on the
Human Development Index – a measure published by the UN that combines with equal weight indicators of a country's health, material living standards and level of education.
In their study – published in
Nature in 2009
54 – they found "a fundamental change in the well-established negative relationship between fertility and development as the global population entered the twenty-first century."
The visualization below shows their finding. Again, we can see the strong negative association between a country’s level of development and the fertility level. But at very high levels of development—HDI over 0.85 or even 0.9—this association is reversed. While causality cannot be established in this relationship, it is evident that after a given point, higher development is associated with increasing fertility. Not only do the authors show this relationship cross-sectionally, but also over time: after reaching the lowest Total Fertility Rate at HDI values between 0.85 and 0.9, fertility then increases again as countries advanced to the highest development levels.
It is a finding with important consequences. The authors note that this reversal "has the potential to slow the rates of population ageing, thereby ameliorating the social and economic problems that have been associated with the emergence and persistence of very low fertility".
For an interactive version of the above visualization, see
here.
The relationship between fertility and HDI through time (1980, 2000, 2014)55
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