The Population Debates

(A) Pre-Malthusian
(B) The Malthus Debate
(C) The Demographic Transition

Robert Malthus's population doctrine -- particularly the wage-fertility dynamics -- were incorporated in Classical economic doctrine by David Ricardo (1817). Ricardo's "iron law of wages" relied almost completely upon it.

However, in the 1820s and 1830s, Malthus's population doctrine fell into disfavor and economists lined up behind each other to denounce it. The main problem was that the Cantillon-Malthusian wage-fertility dynamics upon which it relied was viewed by many contemporary economists as a bit of an over-stretch. Much of the Malthusian debate of the 1830s ended up in quibbling about whether Malthus's doctrines were empirical or theoretical propositions.

(A) Pre-Malthusian

When Robert Malthus published his essay in 1798, the population debate had actually been going on for a while -- but in reverse. Malthus worried about overpopulation; but previous authors, particularly Mercantilists like Petty and Americans like Franklin, had been worried about underpopulation.

Nassau William Senior (1829) was perhaps the most articulate assailant of the Malthus hypothesis. For Senior, the Malthusian doctrines of population were not self-evident nor vindicated by empirical experience.

Robert Torrens (1829, 1834) recanted the Malthusian doctrine and argued that fertility rates declined as per capita wealth increased. Lesser-known writers, such as M.T. Sadler (1830) and G.P. Scrope (1831, 1833) repeated the charge. Richard Whately (1832) and Ramsay McCulloch (1832) joined the critical chorus.

The essence of the debate was empirics. It may be instructive to decipher what the empirical implications actually are. Now, Malthus's hypothesis is that n_p > g, whereas the alternative anti-Malthus hypothesis is that n_p < g. As we cannot observe the natural population growth rate, n_p, we must deduce the empirical implications of Malthus's theory from observations of g and n.

Now, if Malthus hypothesis is true, then, we should expect g » n, i.e. that actual population growth and food supply growth are roughly equal. In contrast, the anti-Malthus hypothesis posits that g > n. Now, according to the empirical evidence, the rate of food supply growth in the 19th Century was greater than the rate of actual population growth. This lends credence to the anti-Malthus hypothesis.

However, this is not the "true" empirical test. As we see in Figure 2, when there is an increase in the rate of food supply growth, then the Malthus hypothesis predicts that g > n for a brief period of time (the lag immediately after time t¢). So, empirical evidence that g > n is not conclusive as it is consistent with both the Malthus and the anti-Malthus hypothesis.

So, a better empirical test lies in examining relationship between changes in food supply growth and actual population growth. In other words, we can try testing the hypothesis indirectly by testing for the wage-fertility dynamics. The Malthus hypothesis predicts that changes in g will be followed by proportional changes in n (cf. Figure 2), whereas the anti-Malthus hypothesis (cf. Figure 3) denies any such connection. However, even this test is imperfect because, under the Malthusian hypothesis, if we are to the left of t* (i.e. if the food barrier has not been hit yet), then g can increase without inducing an increase in n.

The 19th Century Irish situation has often been regarded as an "illustration" of Malthusian dynamics (although Malthus himself never emphasized it). Ireland ended the 18th Century with a population of two million living meagerly on a thin stock of grains. The introduction of the potato, which permitted a much larger yield per acre on Ireland's unforgiving soil, was followed by an expansion of the population in a mere forty years or so to eight million -- exactly as the Malthusian dynamics would have predicted. Then came the blight and the Great Famine of the 1840s -- the "positive check" -- killing off two million, sending another two million abroad and leaving a modest four million behind.

While the Irish experience might seem to vindicate Malthus, the British situation was quite different. From a near-zero growth rate up until around 1700, English population growth had risen dramatically in the course of the 18th Century (with a brief drop during the "Gin Period" of the 1740s). The annual percentage rates of population growth for Britain are approximately the following (averaged over the decade):

c.1750-81	0.6%
1781-91	0.8%
1791-1801	1.2%
1801-11	1.3%
1811-21	1.7%
1821-31	1.5%
1831-41	1.2%
1841-51	1.2%

It was the steady rise in population growth rates from c.1750 to 1820 that inspired Malthus's alarmism. Notice that, all the way through, we are nowhere near the 3% per annum figure implied by Malthus's "geometric progression", implying that the subsistence barrier must have been hit some time before (and thus actual population growth is conforming to food growth). However, the great disturbing factor is that after the 1820s, population growth slowed down. To be fair, Malthus died around this time, and so did not observe this drop. But it places the Malthusian thesis in great doubt. If the barrier was indeed hit beforehand, the only explanation for the decline in population growth after 1821 is that food growth declined. But this is not true. It was precisely around this time that the great gains in agricultural yields and the output of industrial wage goods were being realized.

The final nail in the Malthusian coffin was McCulloch's (1837) empirical findings that the correlation between increasing wages and fertility was spurious. The rising population in Britain in 1750-1820, McCulloch showed, could be mostly accounted for by the decline in the death rate, rather than any increase in the birth rate. As later research has suggested, medical breakthroughs (notably improved midwifery) pushed the death rate slightly below the birth rate. The decline in population growth after 1820 was probably due to the hazards of crowded urban living pushing up mortality again.

Furthermore, McCulloch argued, if we look closely enough, the data showed that fertility rates had actually been falling at a time when England was at its most prosperous. Birth rates -- the great engine of the Malthusian system -- had begun a secular decline in the 1790s which lasted until the 1850s -- exactly at the time of the great agricultural and industrial revolutions. The wage-fertility dynamics are apparently not working.

In sum, the empirical evidence weighed heavily against Malthus's hypothesis on at least three accounts. Firstly, food supply growth has tended to exceed actual population growth (which is more consistent with the anti-Malthus hypothesis than the Malthusian). Secondly, increases in the growth rate of food supply were generally not followed by rising population growth rates (which the Malthus hypothesis can accept only if the food barrier has not been hit yet). Thirdly, when we decompose population growth into birth and death rates, we see that the British population story was carried almost entirely through by fluctuations in the death rate alone. But Malthus's theory had argued that n_p > n, so that any alleviation of the food supply barrier would lead to rising birth rates, rather than declining death rates. On the basis of this evidence, McCulloch (and many of his contemporaries) concluded that Malthus's hypothesis was falsified.

(C) The Demographic Transition

As the Malthusian hypothesis fell into disfavor in the 1830s, contemporary economists, like McCulloch (1828) and Lloyd (1833), were apt to also dismiss policies exhorting "moral restraint" as utterly unrealistic. However, as outlined above, Malthus never suggested that mere preaching solved the problem. The appropriate policy, Malthus argued, was the enbourgoisement of the lower classes, transforming their habits with sticks like the abolition of the Poor Laws and the lifting of labor regulations and with the carrots of political liberty, security of property, education and a taste for a higher standard of living.

In this respect, then, the Malthusians had an escape clause to the mountains of empirical evidence against their fundamental hypothesis. Indeed, if we look at Malthus's policy arguments carefully, in particular the last one about "taste for conveniences", we see the germ of another theory.

A "taste" for a higher standard of living can hardly be brought about unless the lower classes actually experience a higher standard of living. This suggests (although Malthus was not explicit about it) that we may see fertility decline with higher income per capita (or at least a narrower distribution of income). In other words, moral restraint is endogenous to the Malthusian story! Malthus himself had suggested this ambivalence:

This was precisely the theory that was forwarded by Sadler (1830), Torrens (1834), Alison (1840), Doubleday (1841) and Thornton (1846).

The combination of Malthus's own pessimistic theory and the escape clause offered by endogenous "moral restraint" with higher levels of income has been called the demographic transition, i.e. the idea that fertility first increases, and then decreases, with rising per capita income. This is depicted in Figure 4. Up to time t₂, the traditional Malthusian dynamics are at play, but after t₂, the anti-Malthus hypothesis kicks in and population growth grows slower than food supply. The modern model of demographic transition was introduced by Frank W. Taussig (1911: Chs. 52-53), Warren S. Thompson (1928, 1948) and Frank W. Notestein (1945).

The problem with the demographic transition story is that it makes Malthus's hypothesis unfalsifiable. All empirical evidence brought up by McCulloch & Co. does not "contradict" Malthus's hypothesis, but can be explained away by the demographic transition. Thomas Chalmers (1832) and, later on, John Stuart Mill (1848) and Dumont (18??) forwarded precisely such a defense. They did not deny the empirical evidence, but just interpreted it differently. It may be that population growth has declined while incomes per capita rose, they argued, but that just proved that the Malthusian policies and the demographic transition had been working in the interim. The lower classes of Britain, by education and a "taste" for a higher standard of living, had, since the 1830s, been exercising "moral restraint". But that does not deny that, in the past and in much of the remaining world, the Malthus hypothesis remained true. It is worth quoting Mill in full:

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