Johan Fourie's blog

I'd rather be a comma than a fullstop

Fertility explained

with 7 comments

My first empirical paper, written for Murray Leibbrandt’s UCT Stata course, investigated the changes in South African fertility using 2001 census data. I vividly remember struggling to match the textbook definition of fertility with the data that was available in the census and then, while washing the car (and, Helanya, there is no causality here), experienced a Eureka moment and rushed to the computer, soaking wet, to type in the precious code that would give me a semi-decent essay mark.

But fertility is on my radar again. Demographic variables are important because it is correlated with so many development indicators – education, health, and income, of course. Economic historians have also noted its relevance; in fact, when considering a country’s early development performance, demographic variables are often the only reliable quantitative estimates available (see Wrigley 1997). That’s why I found it surprising that there is a total lack of demographic South African history, except for a 1975 paper by Robert Ross using a sample of 300 settler households. Fortunately, a new data set which includes more than 380,000 individuals (compiled from genealogical records by Jeanne Cilliers, a Masters student at Stellenbosch) will begin to provide new answers to questions about early Cape Colony levels of fertility, marriage patterns and household size. More on this soon.

Measuring is only the beginning, though. Understanding the decline in fertility levels worldwide is a topic that have interested economic historians and demographers alike, and is probably one of the ‘big questions’ that are still left without a satisfactory answer. In a new Working Paper by Laura Rossouw, Ronelle Burger and Rulof Burger, this question is again brought to the fore in the context of the South African fertility decline since the 1960s. They use the National Income Dynamics Study data to construct a retrospective panel which allows them to decompose fertility by its causes. They find that a large share of the observed fertility decline across birth cohorts is a result of improving education levels and the lower prevalence of marriage. An important result. However, they also find that a “considerable segment of the transition is ascribed to the unobservables”, i.e. causes we cannot identify. They posit that these include HIV/Aids, the increased use of contraceptives and the social role of women. Yet given that a large part of this decline is in the 1960s and 1970s, it is unclear how important the impact of contraceptives were during this period and how HIV/Aids could have had any role to play.

I’d like to propose another theory, based on the work of Neil Cummins, now at Queens College, City University of New York. In his PhD dissertation on the nineteenth century fertility decline in England and France, Neil posits that:

parents are motivated by relative status concerns and the fertility transition is a response to changes in the environment for social mobility, where upward social mobility becomes obtainable through family limitation. This hypothesis is tested with the new micro data. In both England and France, fertility decline is strongly associated with decreased levels of inequality and increased levels of social mobility. The analysis finds strong support for the role of changes in inequality and the environment for social mobility as central factors in our understanding of Europe’s fertility transition.

Could it be that black South Africans in the 1960s, but especially during the 1970s (when most of Rossouw et al’s fertility decline is unexplained), realised that social and political change is a reality in South Africa, and that those perceptions of social mobility influenced their decision to have children or not? When upward social mobility seemed impossible, more children were always better than fewer because of the greater likelihood of at least one child surviving into adulthood. However, when social mobility became a reality (or perhaps only a perceived reality), fertility decisions changed, as investments in fewer children might allow them to move up the social (and income) ladder. Similarly, white fertility would have been high, given the low risk of downward social mobility during Apartheid. However, once downward social mobility became an option, whites limited their number of children to ensure that their offspring maintain at least the same social status that they enjoyed.

In the wise words of Rafiki: “We can either run from our past, or learn from it.” Time to learn.

PS: Rulof noted below that I misinterpreted their results. The 1960s and 1970s refer to birth cohorts, which means that the largest decline in “unexplained” fertility occurs during the 1980s and 1990s, when these women reach child-bearing age. Their claims about HIV/Aids and contraceptive use therefore make perfect sense. Increased social transfers, also. But Neil’s theory about social mobility, too, has greater relevance, given the political changes South Africa witnessed from 1989 to 1994. The question remains: how to measure “perceived social mobility”?


Written by Johan Fourie

April 24, 2012 at 21:59

7 Responses

Subscribe to comments with RSS.

  1. ” The president also mentions that he was in charge of two wars when he received the peace prize in the first place. He approached them through what he liked to call “preventive diplomacy” and while doing so sought to establish more independence and effectiveness in the post of Secretary-General itself. Little improvements were made up until the 19th century when an American, Charles A.


    November 16, 2012 at 17:33

  2. Thanks for the mention Johan! I think you’re absolutely correct to ask how “perceived social mobility” may be measured – In my thesis I argued that the level of inequality may be used as a proxy (the cross sectional analogue of mobility) – Although the extent to which parent’s can actually accurately gauge this is an issue. My argument was simpler that that though. If we move from a world of very high inequality (with low mobility) to one with lower inequality (and higher mobility) – Fertility decline will kick in via a threshold effect. I think you’re right to add that institutional changes such as the end of apartheid (or indeed the French Revolution) can effect individual’s fertility decisions through perceptions.

    How to rigorously test this? I’m working on that. Along with my co-author Greg Clark, we have formed a sample of individuals with rare English surnames, identified by their economic status in the mid 19th century. As these names are so rare it is possible to construct their complete demographic history from the census and vital registration records. Our first paper using this sample calculated an inter-generational correlation between generations of .7 to .8 (wealth of parents – offspring), far higher than the literature suggests.

    From the mobility-fertility perspective, what is interesting is that this correlation is constant over time (more or less) across the high and low fertility regime in England.

    In future work, I hope to use the individual level data and look at the inter-generational correlation and see if it varies across families with different fertility strategies.

    Neil Cummins

    May 3, 2012 at 03:08

  3. You raise an interesting alternative explanation for the as yet unexplained part of the fertility decline. Just to clarify, the paper finds that the largest part of this decrease did not occur during the 1965-1975 years, but rather for women born in the 1965-1975 period, i.e. women who were at their peak fertility age between 1990-2000. I think this makes both the HIV/AIDS – contraception use explanation and your social mobility story more plausible.

    Rulof Burger

    April 25, 2012 at 09:30

  4. Great post. And even better final quote. I’ll let Neil you wrote about him! Greetings!

    Manuel Bautista

    April 24, 2012 at 22:10

    • I’ll let Neil *know you wrote about him!

      Manuel Bautista

      April 28, 2012 at 19:32

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: