The demographic transition

It has been shown that the population slowdown was the decivise factor in raising productivity.

To analyze this population slowdown in detail, demographers usually decompose its evolution into a reduction of death rates, representing mortality, and a decrease in birth rates, representing fertility. The evolution of these vital rates over the past centuries is commonly conjointly stylized on a national level, illustrating a fourphase model termed as the demographic transition (see Figure 5.1). The model of the demographic transition in the right graph is crudely based on

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the British experience over the period 18002000 as is displayed in the left graph. In phase one, birth rates and death rates display relatively high values. At the beginning of phase two, the death rate declines due to the socalled epidemiological transition, inducing as a byproduct a population explosion, urbanization and sometimes an industrial revolution. In phase three, the birth rate starts to succeed the decreasing death rate, slowing down population growth, until they both settle on an approximately equal low level in phase four.

Figure 5.1: Left graph: British demographic transition: Birth rate (blue) and death rate (red) 18002016.

Right graph: Stylized fact demographic transition.

Sources: Wrigley and Schoeld (1981) for 18001871, Mitchell (2013) for 1871-2010.

Following the national accounts on the demographic transition, it must stare the neutral observer in the face that death rates and birth rates display some inherent connection. When comparing international data on vital rates, no economy can be found in which a sustained decline in birth rates has been realized without a preceding decline in death rates (see Figure 5.1 for Britain and again for numerous examples Appendix 11.2). For this reason, it is impossible not to become impressed with the idea that it appears to be a statistical law that the mortality reduction generally predates the fertility decline. Therefore, demographers have  in contrast to economists  ever since suspected a positive causal eect of changes in mortality on changes in fertility.¹ Although fertility seems to universally react belatedly to mortality, this lag varies strongly across economies, ranging from a few years to more than a century, which led many economists to wrongly shift their attention to the industrial revolution as main trigger for the fertility decline. Nonetheless, several economists also came to the conclusion that diminishing mortality must be causal for the fertility decline and the concomitant increase in GDP per capita.

The currently most cited economic explanation for a positive eect of mortality on fertility relies on the fact that decreasing mortality implies increasing life expectancy. Increased longevity may, for example, again foster human capital accumulation or decrease the time preference rate of individuals. Similar to the model by Galor (2011), where human capital accumulation was induced by technological progress, increasing life expectancy may be assumed to raise the demand for human capital and for child quality at the cost of child quantity.

1 For a discussion see Kirk (1996).

Cervellati and Sunde (2005) as well as de la Croix (2008) alter this [Galor's] setup by arguing that life expectancy rose quickly with productivity. This in turn encouraged investment in human capital, as payback horizons lengthened. Even if technological change is only slightly skillbiased, a selfreinforcing cycle of better technology, greater life expectancy, and higher investment in human capital can get started.²

Such models have been explored more recently by Ludwig and Vogel (2009), Herzer et al. (2012) or Cervellati and Sunde (2017b). As an additional benchmark, Cervellati and Sunde (2011) nd a particularly strong positive correlation between mortality and fertility in those economies where life expectancy exceeds fty years, suggesting a corresponding death rate threshold of about 0.02. The advantage of this group of models lies in their explicit integration of the demographic transition into a unied growth theory. However, as Mokyr and Voth criticize,

models in the Lucas and Becker tradition emphasize the increasing demand for and returns to human capital, when we nd little evidence of this [adding that] returns to human capital, conventionally measured, probably did not increase signicantly before 1870.³

While the above association between mortality and fertility through the channel of human cap-ital may be viewed as an indirect eect, there is growing agreement favouring a direct eect of mortality on fertility. A popular view of a direct mechanism emphasizes parental birth re-placement behaviour when facing high child mortality. In addition to the wellknown theory of infant replacement behaviour  to compensate for high infant mortality  the physiological eect of more rapid conception after early (infantile) deaths and the hoarding eect as an insurance against future high mortality when facing frequent subsistence crises are further direct eects on fertility.⁴ Moreover, Clark even argues in favor of a rather automatic direct eect on the fertility decline due to a selfadjusting social environment as being the more promising approach:

fertility limitation in northwestern Europe had little to do with rational individual calculation and much more to do with social customs. [...] Part of the evidence against conscious contraceptive practices is the lack of patterns in fertility that might be found where there was conscious control of fertility.⁵

As a result, direct eects of mortality might exist which do not rely on parents' conscious deci-sions. Social or religious habits such as the custom of late marriage may be capable of suppressing the potential number of children without conscious parental intervention, whereas a practice of divorces in liberal societies will tend to tear couples apart and impede excessive reproduction.

Perhaps the hitherto best modern account of a potential mortalityfertility causation has been given by Hajnal (1965):

If men had to wait till land became available, presumably a delay in the death of the holders of land resulting from declining death rates would tend to raise the age of marriage [and correspondingly diminish fertility] [...]; this is certainly a hypothesis that merits study.⁶

2 Mokyr and Voth (2010), p. 11.

3 Mokyr and Voth (2010), p. 41.

4 See Kalemli-Ozcan (2002), Weil (2010) and Angeles (2010).

5 Alter and Clark (2010). p. 47.

6 Hajnal (1965), p.133.

Being the authors main subject of research, it will subsequently be attempted to clarify the classical view on the great preventive check and to show that its operation has increased without our eorts as a response to the mortality decline.