To the Editors:

With considerable diffidence, I would like to comment on the article by S. R. Eyre (NYR, November 18). My differences with him may seem trivial, since I do not basically disagree with his conclusion that the medium-term (30 to 100 years) future of the human race looks very bleak. However, I find it close to astonishing that Eyre refers to economics and economists only in passing, and then rather disparagingly as though the only concern of economists was to promote the false god of eternal growth, when his whole article is basically about scarcity and the allocation of scarce resources—which are the subjects which many regard economics as being all about! Thus Eyre seems to castigate most people for assuming, with rigid minds, that life can go on as it has recently; but he seems to assume almost equally rigidly that such things as relative prices will not alter—or that if they do, human behavior will not adapt itself to them. The topic is enormous; let us just mention some very simple criticisms of some of the points:

  1. Population: The growth of population is, as Eyre rightly points out, frightening in its implications. However, it is surely misleading to project present rates of population growth to the end of the twenty-first century. Such projections depend crucially on the stability of, for example, age-specific fertility rates. My impression is that demographers have a worse track record for predicting changes in fertility rates than economists have for predicting changes in GNP growth rates. It is also clear that in highly urbanized, industrialized societies, these rates are highly unstable, and react (in ways not fully understood) to changes in economic and social conditions. It should further be noted that one could assert, on the basis of the experience of the past decade,1 that rapid urbanization and industrial growth are the best hope there is for attaining slower population growth in poor countries by means of lower fertility rates (rather than by higher mortality rates, which are the implicit eventual outcome otherwise).
  2. Food: Eyre evidently disagrees with Colin Clark.2 Although I would tend to side with Eyre rather than with Clark, it would be wrong to suggest that there are not reasonable differences of opinion on this subject, and that the calculations of the “optimists” such as Clark—which suggest that the world is capable of feeding an enormously large population—are not careful, considered calculations which take into account such things as differences in soil quality, climate, etc. Even the FAO, which many observers regard as inherently pessimistic on this subject, seems to believe that it is technically feasible to provide adequate food for the expected world population in 1985.3

Furthermore, Eyre ignores the potential of technological change in agriculture, in particular changes in the genetic characteristics of common crops—the familiar “Green Revolution.” Although it is abundantly obvious that the new, high-yielding, high-protein varieties of crops which are being and have been developed will create large and difficult social, economic, and administrative problems if their use is to become widespread; and although it is also true that such widespread use could lead to the disappearance of much of the extant potential “gene-bank” for the crops in question (because local varieties will become extinct unless action is taken to preserve them); it nevertheless is surely wrong to ignore the impact of such changes on the world’s agricultural potential.

More important, however, is Eyre’s blind spot about what may happen to prices for foodstuffs relative to prices for other goods. He does mention that the poor countries with food deficits may not be able to afford to buy the food surpluses of rich countries; but he seems to not notice that, at least to a first approximation, if food is going to become relatively scarcer, it will also become relatively more expensive; and in this situation, how can we justify saying now that agriculture will “not pay” on a particular piece of land at some date in the future?

  1. Natural Resources: Ignoring the implications for relative prices of his predictions of increasing scarcity enormously damages Eyre’s discussion of fuels, metals, other minerals, and the prospects for industrialization in the poor countries. Two points are crucial here. Firstly, although the less developed countries consume very small proportions of world output of fuels, metals, phosphates, and other minerals, they possess sizable proportions of the remaining known and conjectured in-ground deposits of many of these raw materials (oil, tin, copper, and bauxite are obvious examples). As these materials become progressively relatively more scarce (and in many cases, this effect will not be noticeable for a good number of decades), their prices (relative to, say, the labor services of skilled Westerners) should become higher. Thus to some extent the less developed countries which do possess such resources will benefit from the continued growth of population and income in the rest of the world.

Secondly, such overwhelming proportions of these materials are currently consumed in the rich countries precisely because an overwhelming proportion of industrial output is now located in those countries. However, as the rich countries grow richer, their consumption of most raw materials does not grow as fast as their real GNP (energy is another matter). Industry has shown itself to be very adept at finding ways to substitute one material for another when relative prices change, and to reduce the use of expensive materials (compare the thickness of the layer of tin on a can made now with that on a can made thirty years ago; and note also that many cans are now made of aluminium). There is no obvious reason why this process of technological change should not continue; and since in any case the rich countries are tending to consume more services as they get richer, rather than more material goods, one might predict that a time will come when (except for energy) increases in GNP per head in the rich countries may even be associated with falls in consumption of raw materials per head.

It is perhaps significant that the representatives and advocates of the poor, mineral-exporting countries more often talk about these phenomena, and the consequent weakness of the prices of their raw material exports, than about the bonanza they will reap as a result of the lack of raw materials in the world. As a digression, it should be admitted that the processes of substitution and economizing on use of scarce raw materials have, to date, had a number of serious deleterious side effects—“external diseconomies”—particularly on the quality of the environment. But this only bears witness to the fact that society as yet has not been willing to make its members pay cash for the privilege of despoiling the environment—something which it appears we are now becoming more willing to do.

  1. Man as Pest: Economists are not given to making long-term predictions—perhaps because they are frequently forcibly reminded that even their short-term predictions are usually inaccurate. But perhaps they should; or at least they should talk more to the people who do. For what the public attention on questions like population growth and environmental damage presumably is trying to achieve is more attention on the question of how the world will develop during the expected life-span of a child born now. It is highly questionable whether there is any point in trying to make anything approaching a detailed prediction for more than a few years into the future.

On the other hand, we clearly do need some sort of general perspective on how the world may change over the next sixty or seventy years; and when we perform such exercises, we should use all the available, appropriate tools. We will still be wrong; I do not believe that anyone in 1900 could have predicted 1970 very well; but we will be closer to the truth. I do not claim that I am closer to the truth than Eyre; this discussion is far too simplistic to support such a claim. But I do hope that I have suggested reasons why Eyre may be wrong to fear the consequences of “swarming” will be as catastrophic for the human species as for others. I also see the outlook as bleak. Possibly what will happen is that the populations of the rich countries will come to accept static or declining levels of material consumption, and will consume greater and greater quantities of non-material services. In the poor countries, most people will remain horrifyingly poor; but undoubtedly more and more of them will live in towns and this may slow population growth quite markedly; the poor countries will inevitably become more industrialized; and I hope this will allow them to enjoy slowly growing levels of per head material consumption, albeit painfully slowly.


This scenario is probably wildly inaccurate, but I find it somehow too pessimistic, placing too low an assessment on the adaptability of the human species, to predict a sudden, catastrophic decline in total population. Eyre is surely right to appeal for more people to think about the long run, even if as Keynes said we will all be dead then, and to appeal for the abandonment of the rigid thinking (or nonthinking) which assumes we can progress as we have in the recent past without limit into the future. But it is just as rigid, and perhaps just as dangerous, to assume that relative prices, and human behavior, will not react and adapt to changes in population/land and population/resource ratios.

James H. Cobbe

Department of Economics

Yale University

New Haven, Connecticut

S. R Eyre replies:

I would like to make my apologies to Mr. Cobbe and to all economists who are genuinely alarmed about the material plight of the human race if I have appeared disparaging in my references to economists generally. In my defense I can only assure him that, when preparing my paper. I felt obliged to seek out the works of economists who had done some positive thinking about the population/resources crisis. In particular I asked a number of professional economists if they could refer me to recent works which explored the problems of organizing a national economy in face of a shrinking population. None was forthcoming. Indeed the only works to be found in this general field were products of the 1930s and early 1940s which were written in the light of the slowing rates of increase in Western Europe at that time and which viewed the phenomenon of population decline with alarm and repugnance.4 I am sure that Mr. Cobbe would agree that difficult economic problems will have to be solved when population controls begin (hopefully) to be applied with consequent alteration of age structure. It seemed to me that one has a right to expect that forward-looking economists might already have begun to supply some guidelines.

It is always difficult to reply effectively to someone who admits to being half in agreement with you, particularly if he answers mainly quantitative arguments in rather qualitative terms, but I would like to take up the main points of criticism that have been made.

  1. Population: I feel I can justifiably refuse to enter into debate on the instability of fertility rates. For half a century or more some demographers have tended to shoot from behind a smoke screen of complexity and minutiae when the danger of world overpopulation has been mentioned. Armed with their skills in arguing about fertility rates, they succeeded in pouring scorn on the simplistic views of “Neo-Malthusians.” In spite of demographers, however, world population as a whole has been increasing rapidly and uninterruptedly for a long time and it would be a great coincidence if this trend were to change radically, for sporadic reasons, just as we are reaching the point (quite unperceived by the majority of mankind) where pressure on total global resources is becoming critical. To suggest, then, that we should pin our faith on urbanization and industrial growth is surely unreasonable. Since the beginning of the Industrial Revolution, over 150 years ago, the population of Britain has risen from less than 10 million to more than 50 million and it is still rising. Even to hint that we might commit ourselves to “rapid urbanization and industrial growth…” on “…the experience of the past decade…” is bordering on irresponsibility, even if only because of the instability of fertility rates that Mr. Cobbe has referred to.
  2. Food: In an essay which dealt with the world picture of human ecology it was inevitable that many important topics could not be mentioned specifically. The “Green Revolution” was one of these. I would only like to say that, quite apart from the great dangers inherent in an enormous extension of monoculture of relatively untried, exotic crops, the successful implementation of such a “revolution” demands high fertilizer input and the fallacies of a “fertilizer-intensive” agriculture for the technology-deficient peoples were noted in my article.

As for the view that, as food becomes scarcer, prices for it will rise and thus make agriculture profitable on relatively poor soils, I can only ask who is going to pay these higher prices? With this kind of argument it is very difficult to explain why there are so many millions of starving and grossly undernourished people in the world today along with so much uncultivated land. The fact that there are both indicates to me that sustained-yield agriculture will never occur on many poor soils, unless we can achieve an opulent world with ample elbow room in terms of resources. In such a world, of course, there would be no need to cultivate land anyway!

The problem of world food shortage is so pressing that scientists should say nothing which will confirm administrations in their comfortable illusions about the high potentialities of the world’s soils. I am pleased that Mr. Cobbe “tends to side with” me rather than with Colin Clark; this being the case, how nice it would be if he were to devote his energies to a search for solutions rather than to an exposé of my “blind spots,” numerous though these may be.

  1. Natural Resources: My chief “blind spot” has been diagnosed as an inability to appreciate the implications of relative prices, the point being that it is a basic precept of economics that as a commodity increases in scarcity its price will rise relative to prices of other things. May I respond by pointing out that in the population/resources crisis we are not ultimately concerned with scarcity but with exhaustion or nonavailability. To illustrate the point may I postulate an entirely theoretical, nonexistent metal called exwy-zedium which has unequaled physical and chemical properties which would make it an unrivaled commodity in thousands of industrial processes and products. I would like to ask the economists what is the price of this commodity, and what is the price when halved or doubled? It matters not whether they reply “nil” or “infinity”—the substance is nonavailable so that any debate is quite academic.

Given present trends, in fifty years’ time the only difference between exwyzedium and things like mercury, lead, platinum, zinc, gold, silver, tin, copper, tungsten, molybdenum, nickel, aluminium, cobalt, and manganese will be that the former has never been available whereas the latter have, but have ceased to be so.5 Vast industries will not have developed which are dependent on exwyzedium. Furthermore, it is vain to speak of substitution if, over the short period involved, all known alternatives are being worked out. The main concern of all scientists and technologists who think in quantitative terms is not that there are going to be industrial stresses and strains in 1972—it is that industry and society in general are going to proceed in their old ways for another quarter of a century on the strength of materials which are still plentifully available. They will thus gobble up resources at a rate of increase of 6 percent per annum and whether there are individual increases and decreases because of substitution does not affect the argument at all.


The result will be a doubled world population by the end of the first decade of the twenty-first century the vast majority of which are urban and dependent on industries and services which, in turn, are dependent on metals. Furthermore, as Mr. Cobbe says, the less developed countries which today possess valuable minerals will certainly benefit from their increased scarcity while they last, but if populations and urban areas in these countries grow apace on the strength of these temporary advantages, the crash and the disappointment will be all the greater when exhaustion comes. I do not know exactly what Mr. Cobbe is visualizing when he speaks of the possibility of populations in richer countries accepting declining levels of material consumption and consuming “greater and greater quantities of nonmaterial services”; I am merely very perplexed by his vision of industrialization and urbanization as a means whereby peoples in poor countries can come to “enjoy growing levels of per head material consumption.” unless he is thinking merely of the next twenty or thirty years.

  1. Man as Pest: No reasonable person would deny that man’s mental development makes him different from all other animals, but unfortunately many aspects of his behavior in the mass appear to conform very closely to those of animal populations. In particular the natural urge to reproduce at more than replacement rate is possessed by Homo sapiens just as it is by all other thriving species. When the natural controls of disease and disaster are much reduced, this automatically leads to “swarming.” Man has emancipated himself from natural controls by purposefully applying his mind to environmental control, so it seems to me that his only reasonable chance of evading the outcome is by a conscious and purposeful reduction of births. The whole tenor of Mr. Cobbe’s response to my article seems to imply that we must go on just hoping that some quirk of social development (urbanization, increased standard of living, and so on) will, indirectly, produce the desired results.

Students of biology, because of the nature of their training, seem to see these issues clearly enough; my pessimism arises mainly out of the fact that most educated people, including many social scientists, are so anthropocentrically disposed that they cannot appreciate them. This being the case, what hopes can we entertain for those who do not have the advantages of education but who, after all, carry out most of the reproducing?

This Issue

February 24, 1972