Posts tagged cohort fertility
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.

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Fertility and sexual selection

Markets are moving, and I’ll have more to say about that in due course, but we before we get to that, I am finally ready to present the third chapter in my running demographics project. The landing page for the project can be found here. You can get the PDF for the third chapter below, or via the landing page.

This chapter kicks off the description, analysis and discussion of fertility and birth rates. It is the first of, I suspect, three chapters on fertility. In it, I try to cover three bases. First, I cover the basics, defining the different ways in which fertility and birth rates are described quantitatively in the literature, and the distinction between these terms. Secondly, I summarise the stylised facts about the global fertility transition, when it began, and how it is going. My objective has been to strike a balance between the big picture and sufficient detail to allow for the discussion individual case studies across individual nations, or groups of countries. The key point, from both an empirical and theoretical perspective, is that fertility does not stabilise at replacement levels in the final stages of the demographic transition. In this way, the fertility transition is an ongoing phenomenon, in contrast to the picture painted by the stylised model of the demographic transition. Thirdly, I run through the theory of sexual selection as described by Trivers (1972), and used in Richard Dawkins’ seminal, The Selfish Gene. There are two reasons for this. First, the basics matter. The game of mate selection, which feeds through to how parents share the costs of reproduction and child-rearing, is crucial to understand why births occur in the first place. The idea that evolved behaviour described by Trivers (1972) can be used to explain phenomena in a modern context invites us to heed F. Scott Fitzgerald’s advice that “the test of a first-rate intelligence is the ability to hold two opposing ideas in mind at the same time and still retain the ability to function.” It is reasonable to expect that many phenomena observed in a modern society can be traced back to core evolutionary processes. But equally, it is unreasonable to go searching for an evolutionary explanation for every phenomenon that social scientists might be interested in, in a modern economy. Whatever the balance between these two positions, the link between modern behaviour and pre-modern evolutionary theorems is a constant source of debate and controversy in the literature on demographics and fertility.

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