^1. J. Bourgeois-Pichat, "Essai sur la mortalité biologique de l'homme," Population, No. 3 (I952).

^2. J. Fourastié, "Recherches sur le calendrier démographique de l'homme moyen de la vie traditionelle à la vie ‘tertiaire,' " Population, No. 3 (I959).

^3. E.g., E. Gautier and L. Henry, "La Population de Crulai, paroisse normande," I.N.E.D. Cahier, No. 33, I958.

^4. The symbol e ₀ indicates the life-expectancy at birth, that is to say, at age o. One can, indeed, calculate the life expectancies at different ages, which one then indicates by e ₁₀, e ₂₅, etc. (average number of years to live for those reaching the ages of I0, 25, etc.).

^5. The United Kingdom was able to break away from the traditional situation a little earlier; but a half-century, more or less, is not important in this matter.

^6. Cf. J. Fourastié, "Le Personnel des enterprises, remarques de démographie et de socio logie," Population, I960.

^7. Villermé, Tableau de l'état physique et moral des ouvriers des manufacturers de coton, de laine et de soie, XI, 25I, 375.

^8. The figures published by the United Nations are as follows: high estimate, 6.9 billion; mean estimate: 6.28 billion; low estimate: 4.88 billion (United Nations, Études de popula tion, No. 28 [New York, I958]).

^9. The densities of these countries are calculated here on their total geographic area. It is clear that a great part of these lands is only effectively cultivable and habitable in a hypoth esis similar to Hypothesis B.

^10. It can be seen that Hypotheses A and B, which are so different from each other in the technical and geographical point of view, differ very little in the demographic viewpoint.

^11. A complete family is a family in which both parents are living at least until the mother reaches the age of 50.

^12. A. Sauvy, Théorie générale de la population.

^13. "The man worth forty crowns: How many arpents do you think there are in France? —The geometrician: One hundred and thirty million, of which almost half [55 million hectares] are (sterile)…. The land with a good yield could be reduced to seventy-five million square arpents; but let us count it as eighty million…. How much do you estimate every arpent yields on an average, in the average year, in wheat, all sorts of grain, wine … cattle, fruit, wool, silk, milk, oil: … The geometrician: If each produces twenty-five pounds it is a lot" (Voltaire, L'Homme aux quarante écus, in Contes et Romans, III ["Les textes français"] (Paris: L'Association Guillaume Bude)]), pp. I6 ff.

Twenty-five pounds represented at the time the average price, over a long period, of a quintal of wheat. The total production of France's soil was thus the equivalent of 80 million quintals of wheat, say, 4 quintals per head of the population (one kilogram per day and per person). It can be understood that nourishment was close to its limit. For a closer examination of the question see my book Machinisme et bien-être, pp. I40 ff.; in English, The Causes of Wealth (Glencoe, Ill.: Free Press, I960), pp. I42 ff.

^14. Of course, discussion is usual to establish whether the problem of food is effectively solved or whether, on the contrary, the underdeveloped countries are not going toward new famines; but this has been debated very often, and I have no new items to add to the dossier. That is why I prefer to deal with the following problem: Supposing the problem of food to be solved, are there other unconscious and coercive mechanisms to limit the number of human beings? It does appear to me to be established that the problem of food is about to be effectively overcome, that is to say, taken over two or three centuries (especially if one thinks about the cultivation of the sea).

^15. 550 million are equal to the density of ten to the hectare; with the density one hun dred it would be 5,500 million. This calculation is of interest even for figures on the order of I00 million.