Many countries, including almost all developed countries and many developing countries, are now experiencing below-replacement fertility, with fertility rates having declined substantially over the past decade or more. That means that each generation will be progressively smaller than the last, and almost inevitably that leads to a declining population (in the absence of offsetting migration flows). Can countries reverse the trend of declining fertility, and return to replacement levels? Two new articles suggest that might be difficult.
The first is this article by Michael Geruso and Dean Spears (both University of Texas at Austin), published in the Journal of Economic Perspectives (open access). They look explicitly at the question of whether persistently low fertility can be reversed, but first they do a great job of setting the scene:
Fertility is low or falling across the world: among high-, middle-, and low-income countries; among secular and religious populations; and in economies where the state is large and where it is small. Birth rates have been falling not only for decades, but for centuries. They have been falling for as long as there are good historical records to document them...
The TFR [total fertility rate] has fallen from a global average that was a little under five in 1950 to a global average that is a little over two in 2025...
The 115 richest countries in the world together have an average total fertility rate of 1.5... A birth rate of 1.5 would lead to a decline of 44 percent in generation size over two generations...
Geruso and Spears then look at the trends in some detail, focusing attention on completed cohort fertility (CCF), which captures the average number of lifetime births for women born in a particular place and year. That is a better measure than the TFR, because it is not affected by the timing of births - a woman having two children at ages 25 and 34 instead of aged 25 and 27 would not change the CCF, but would affect the TFR in the years in which they gave birth (increasing TFR when they were aged 34, but decreasing it when they were aged 27). In any case though, the trends in the two measures (CCF and TFR) are broadly similar, with both showing declining fertility over time across all of the countries that Geruso and Spears consider (with the exception of the US in the 1980s to 2000s, where there was a modest increase in fertility).
Geruso and Spears then use global data from the Human Fertility Database (HFD), and Indian data from the National Family Health Survey, and explore the contribution of childlessness to the overall decline in fertility. In both datasets, they find that the majority of the decline in fertility is due to a decline in the number of children among women who have at least one child, rather than an increase in childlessness. For countries in the HFD, childlessness accounts for 37 percent of the decline in fertility between the cohort of mothers born in 1956 and the cohort born in 1976, while in India, childlessness accounts for just 9 percent of the differences in fertility across districts.
Finally, Geruso and Spears turn to the prospects for a reversal of the fertility trend. On this, they start by noting that in the HFD:
...there have been 24 countries in which cohort fertility ever fell below 1.9. In none of these cases have subsequent cohorts from the same country ever had fertility as high as 2.1...
And aside from the post-WWII Baby Boom, there are no significant episodes of increasing fertility. And the Baby Boom was the result of a fairly unique set of circumstances that are (hopefully) unlikely to be repeated. Geruso and Spears then look at the microeconomic and programme evaluation literature, and note that:
...the clear-cut bottom line is that whatever impacts pro-natal policies and broader changes might have caused, none has caused low birth rates to reverse enduringly back to replacement levels.
Even a particularly strict programme in Romania that "banned abortion and made modern contraception effectively inaccessible" had only a short-term effect on the total fertility rate, and no effect on completed cohort fertility. So, this paper gives no reason to believe that declining fertility can be reversed. Geruso and Spears conclude that:
To put it bluntly, history offers no examples of societies recognizing very low birth rates as a social priority and then responding with effective changes that restore, and sustain, replacement-level fertility.
The second article is this one by Kimberly Babiarz (Stanford University), Paul Ma (University of Minnesota), Grant Miller (Stanford University), and Shige Song (City University of New York), forthcoming in the journal Review of Economics and Statistics (ungated earlier version here). They don't look explicitly at fertility decline, but they do look in detail at fertility in China, and in particular at the impact of the Wan Xi Shao (Later, Longer, Fewer) campaign, which predated the One Child Policy. That policy:
...aimed to limit fertility by promoting older age at marriage (“Later”), longer intervals between births (“Longer”), and fewer births per couple (“Fewer”).
The campaign was very successful, with the total fertility rate falling from 6 to about 2.75 over the course of the 1970s. The One Child Policy began in 1980, so by the time it was instituted, China's fertility had already fallen almost to replacement level. Babiarz et al. aren't the first to note this, but they extend the analysis further, exploiting differences in the timing of implementation of the policy across Chinese provinces to investigate how much of the decline in fertility was due to the policy, how it affected fertility decisions within Chinese families, and how many 'missing girls' are attributable to the policy implementation in combination with a societal preference for sons.
Now, as a policy the LLF aimed to:
...reduce crude annual birth rates in rural areas to 15 per 1,000 population via three primary mechanisms: (1) later marriage—delaying marriage to ages 23 and 25 (for rural women and men respectively); (2) longer birth intervals—increasing birth intervals to a minimum of four years; and (3) fewer lifetime births—limiting couples to 2–3 children in total...
The policy was implemented differently in urban areas, and about 87 percent of births in the sample occurred in rural areas, so Babiarz et al. focus attention on births in rural areas. Their main data source is the 1988 Two-per-Thousand National Survey of Fertility, which was a nationally representative survey that included around 400,000 women living in rural areas. I'm not going to go into detail on their methods (you should read the paper), but using an event study design, they find that the policy:
...reduced China’s total fertility rate by almost one birth per woman, accounting for about 30.6% of China’s overall fertility decline prior to 1980, or approximately 18.2 million averted births... Decomposing this TFR change into “quantum” and “tempo” effects, we show that, although the policy raised mothers’ median age at first birth by 5.2 months, the decline in TFR was largely the result of fewer lifetime births rather than changes in the timing of births.
They also find that:
...the LLF policy led directly to an increase in the use of both male-biased fertility-stopping rules and postnatal selection (via neglect or possible infanticide). Although postnatal selection was relatively rare, our results imply that the LLF policy resulted in about 180,000 additional missing girls, or approximately 19% of all missing girls during the 1970s.
So, the policy was quite successful in reducing Chinese fertility faster than it otherwise would have. However, this came with the unintended consequence of fewer female births relative to male births, and the phenomenon of 180,000 'missing girls' (who would have been born if the policy had not been in place).
How does this relate to the Geruso and Spears article, and what does it tell us about changing fertility? The Babiarz et al. article shows what it takes to move fertility quickly, but only in one direction (downwards). The LLF policy was dramatic, and successful, but it took a concerted government effort, supported by severe penalties, to achieve its aim. And this was in an environment where fertility was already declining. That's a very different challenge from trying to engineer a sustained increase in fertility back to replacement levels.
So, where does that leave us? If we have essentially no historical examples of societies successfully and sustainably reversing very low fertility, then the practical policy question shifts to planning for a future with progressively smaller age cohorts and older populations. That may mean reconsidering institutions that rely on a foundation of population growth (retirement and superannuation, and health and long-term care), as well as family-friendly policies and immigration settings. Policy proposals that treat women as a demographic instrument (like this one) aren’t a solution - they’re a warning sign that we’re asking policy to do something it may not be able to do.
[HT: Marginal Revolution, for the Babiarz et al. article]
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