Delayed Gratification - Why are global birth rates falling, and does it matter?

This is the final chapter in the first part of my long-running demographics project. In the previous chapter I described the quantum effect of fertility, which hypothesises a negative relationship between fertility and rising incomes as parents substitute quantity for quality in their reproductive decisions and child-rearing. But can the quantum effect explain why birth rates in one country after the other appears to be stuck below the replacement level, and why global fertility will soon drop below that same level? The answer is no.

To understand current and more recent post WWII global fertility trends—broadly since the 1970s—we need to introduce tempo effects to the analysis. Tempo effects describe the tendency of women to postpone the timing of their first child. By mathematical logic, prolonged tempo effects can drive significant population ageing, but a more fundamental question is whether birth postponement also has a lagged effect on quantum, or more precisely, cohort fertility. This chapter discusses these question in the context of the hypothesis of a Second Demographic Transition, SDT, and presents a number of case studies to explore the specifics of recent fertility trends in key countries and regions. The chapter finishes by discussing the idea of a fertility trap, and whether the increasingly accelerating decline in global birth rates are a problem, drawing on the recent polarisation in the debate on this issue.

The PDF of the chapter can be found here.

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Below is a blow-by-blow Twitter/X-thread of the chapter’s main conclusions and points.

In my previous essay on demographics, I described the quantum effect of fertility. In this chapter, https://bit.ly/43k2kqK, I describe the tempo effect , captured by the rise in birth postponement since the 1970s in one country after the other. 1/19.

An analysis of the tempo effect of fertility occurs in the framework of the 'Second Demographic Transition', SDT. It is inquiry into birth postponement, and an analysis of how and why low period fertility feeds through to cohort fertility over time. 2/19

The SDT has three components. 1) A shift towards self-realisation, linked to a rise in the relative return of somatic investment, especially for women. 3/19

2) A decline in living standards relative to expectations, forcing couples to postpone or forgo childrearing. 3) The transmission of a low-fertility ideal via cultural evolution pathways. 4/19

The SDT's key predictions are; a rise in the mean-age of first child birth, a fall in marriage rates, a rise in fertility control via contraception, a break in the link between sex and reproduction, a falling ideal fertility rate and a rising incidence of childlessness. 5/19

These predictions are supported by empirical evidence, but the experience across countries differ. The SDT was conjured with European data. Its main driving forces are mediated by initial conditions of culture, social values and economic conditions in individual countries. 6/19

The chapter includes numerous case studies; the conclusion broadly is that tempo effects are re-accelerating, further entrenching sub-replacement level fertility in one country and region after the other. Global period fertility will soon fall below two. 7/19

Do some countries risk falling into a fertility trap? In the early 2000s, the literature hypothesised the risk of a fertility trap, when period fertility drops below 1.5, and argued that public policy should attempt to prevent such an outcome from becoming entrenched. 8/19

The fertility trap has three components; 1) negative population momentum. Very low fertility reduces the future pool of mothers, perpetuating a fall in births over time. 9/19

2) A sustained period of low fertility can entrench a low fertility ideal through cultural evolution. 3) A fall in income expectations relative to economic aspirations. 10/19

Is the fertility trap real? By the 2010s, many researchers concluded that it isn't as binding as initially feared as fertility rates were rebounding in many European countries. Now, however, it seems relevant to ask the question again. 11/19

Negative population momentum is real. A sustained period of below-replacement fertility will shrink the pool of future mothers, driving down the absolute number of births over time. Once in motion, this process is difficult to stop. 12/19

The two other components of the fertility trap are contradictory. One seems positive; a conscious choice by women to have fewer children that perpetuate through cultural evolution. The other is negative; a fall in income expectations relative to initial economic aspirations. 13/19

Both the positive and negative drivers of falling fertility can operate at the same time across different groups in society. If they do, we should expect fertility to fall rapidly and to very low levels in some countries. 14/19

Is low and falling fertility good or bad? Modern market-economies with tax-payer funded healthcare and pensions work best with fertility close to replacement level. Failing that, the cost of population ageing increases over time, substantially. 15/19

The debate on falling birth rates is now polarised. It pits a neo-Malthusianism—linked to climate change fears—with a Neo-conservative view that low birth rates reflect fundamental flaws, and maladaptive traits, in society. 16/19

What happens next? The global total fertility rate will soon fall below 2, due to a large part to accelerating tempo effects. This invariably will have a lagged effect on quantum effects and cohort fertility. 17/19

A decline in global period fertility to below the replacement level will further entrench positions. The culture wars have descended on the demographics discipline. Scholars and researchers must keep their cool. Many won't. 18/19

The end. Find previous chapters and the list of references for all chapters - > https://bit.ly/3S0em4Q. cc: @VSkirbekk, @tavitonst, @nonebusinesshey, @MoreBirths, @MartinKolk and @alisongemmill 19/19